michaelmcgurk michaelmcgurk - 2 months ago 12
CSS Question

Change section background colour for each loop in an image slider

I have a very simple slider on my home page which loops through different images.

To spice things up, I wonder is it possible to change the

background-color:
value of the
cd-hero
section each time a new image is loaded up? Can I store this in an array so the first image loads a red background and the 2nd image loads blue and so on?

Demo: https://jsfiddle.net/12dd5j1s/



jQuery(document).ready(function($){
var slidesWrapper = $('.cd-hero-slider');

//check if a .cd-hero-slider exists in the DOM
if ( slidesWrapper.length > 0 ) {
var primaryNav = $('.cd-primary-nav'),
sliderNav = $('.cd-slider-nav'),
navigationMarker = $('.cd-marker'),
slidesNumber = slidesWrapper.children('li').length,
visibleSlidePosition = 0,
autoPlayId,
autoPlayDelay = 5000;

//upload videos (if not on mobile devices)
uploadVideo(slidesWrapper);

//autoplay slider
setAutoplay(slidesWrapper, slidesNumber, autoPlayDelay);

//on mobile - open/close primary navigation clicking/tapping the menu icon
primaryNav.on('click', function(event){
if($(event.target).is('.cd-primary-nav')) $(this).children('ul').toggleClass('is-visible');
});

//change visible slide
sliderNav.on('click', 'li', function(event){
event.preventDefault();
var selectedItem = $(this);
if(!selectedItem.hasClass('selected')) {
// if it's not already selected
var selectedPosition = selectedItem.index(),
activePosition = slidesWrapper.find('li.selected').index();

if( activePosition < selectedPosition) {
nextSlide(slidesWrapper.find('.selected'), slidesWrapper, sliderNav, selectedPosition);
} else {
prevSlide(slidesWrapper.find('.selected'), slidesWrapper, sliderNav, selectedPosition);
}

//this is used for the autoplay
visibleSlidePosition = selectedPosition;

updateSliderNavigation(sliderNav, selectedPosition);
updateNavigationMarker(navigationMarker, selectedPosition+1);
//reset autoplay
setAutoplay(slidesWrapper, slidesNumber, autoPlayDelay);
}
});
}

function nextSlide(visibleSlide, container, pagination, n){
visibleSlide.removeClass('selected from-left from-right').addClass('is-moving').one('webkitTransitionEnd otransitionend oTransitionEnd msTransitionEnd transitionend', function(){
visibleSlide.removeClass('is-moving');
});

container.children('li').eq(n).addClass('selected from-right').prevAll().addClass('move-left');
checkVideo(visibleSlide, container, n);
}

function prevSlide(visibleSlide, container, pagination, n){
visibleSlide.removeClass('selected from-left from-right').addClass('is-moving').one('webkitTransitionEnd otransitionend oTransitionEnd msTransitionEnd transitionend', function(){
visibleSlide.removeClass('is-moving');
});

container.children('li').eq(n).addClass('selected from-left').removeClass('move-left').nextAll().removeClass('move-left');
checkVideo(visibleSlide, container, n);
}

function updateSliderNavigation(pagination, n) {
var navigationDot = pagination.find('.selected');
navigationDot.removeClass('selected');
pagination.find('li').eq(n).addClass('selected');
}

function setAutoplay(wrapper, length, delay) {
if(wrapper.hasClass('autoplay')) {
clearInterval(autoPlayId);
autoPlayId = window.setInterval(function(){autoplaySlider(length)}, delay);
}
}

function autoplaySlider(length) {
if( visibleSlidePosition < length - 1) {
nextSlide(slidesWrapper.find('.selected'), slidesWrapper, sliderNav, visibleSlidePosition + 1);
visibleSlidePosition +=1;
} else {
prevSlide(slidesWrapper.find('.selected'), slidesWrapper, sliderNav, 0);
visibleSlidePosition = 0;
}
updateNavigationMarker(navigationMarker, visibleSlidePosition+1);
updateSliderNavigation(sliderNav, visibleSlidePosition);
}

function uploadVideo(container) {
container.find('.cd-bg-video-wrapper').each(function(){
var videoWrapper = $(this);
if( videoWrapper.is(':visible') ) {
// if visible - we are not on a mobile device
var videoUrl = videoWrapper.data('video'),
video = $('<video loop><source src="'+videoUrl+'.mp4" type="video/mp4" /><source src="'+videoUrl+'.webm" type="video/webm" /></video>');
video.appendTo(videoWrapper);
// play video if first slide
if(videoWrapper.parent('.cd-bg-video.selected').length > 0) video.get(0).play();
}
});
}

function checkVideo(hiddenSlide, container, n) {
//check if a video outside the viewport is playing - if yes, pause it
var hiddenVideo = hiddenSlide.find('video');
if( hiddenVideo.length > 0 ) hiddenVideo.get(0).pause();

//check if the select slide contains a video element - if yes, play the video
var visibleVideo = container.children('li').eq(n).find('video');
if( visibleVideo.length > 0 ) visibleVideo.get(0).play();
}

function updateNavigationMarker(marker, n) {
marker.removeClassPrefix('item').addClass('item-'+n);
}

$.fn.removeClassPrefix = function(prefix) {
//remove all classes starting with 'prefix'
this.each(function(i, el) {
var classes = el.className.split(" ").filter(function(c) {
return c.lastIndexOf(prefix, 0) !== 0;
});
el.className = $.trim(classes.join(" "));
});
return this;
};
});

/* http://meyerweb.com/eric/tools/css/reset/
v2.0 | 20110126
License: none (public domain)
*/

html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed,
figure, figcaption, footer, header, hgroup,
menu, nav, output, ruby, section, summary,
time, mark, audio, video {
margin: 0;
padding: 0;
border: 0;
font-size: 100%;
font: inherit;
vertical-align: baseline;
}
/* HTML5 display-role reset for older browsers */
article, aside, details, figcaption, figure,
footer, header, hgroup, menu, nav, section, main {
display: block;
}
body {
line-height: 1;
}
ol, ul {
list-style: none;
}
blockquote, q {
quotes: none;
}
blockquote:before, blockquote:after,
q:before, q:after {
content: '';
content: none;
}
table {
border-collapse: collapse;
border-spacing: 0;
}






/* --------------------------------

Primary style

-------------------------------- */
*, *::after, *::before {
-webkit-box-sizing: border-box;
-moz-box-sizing: border-box;
box-sizing: border-box;
}

html {
font-size: 62.5%;
}

body {
font-size: 1.6rem;
font-family: "Open Sans", sans-serif;
color: #2c343b;
background-color: #f2f2f2;
}

a {
color: #d44457;
text-decoration: none;
}

img {
max-width: 130%;
}

/* --------------------------------

Main Components

-------------------------------- */
.cd-header {
position: absolute;
z-index: 2;
top: 0;
left: 0;
width: 100%;
height: 50px;
background-color: #21272c;
-webkit-font-smoothing: antialiased;
-moz-osx-font-smoothing: grayscale;
}
@media only screen and (min-width: 768px) {
.cd-header {
height: 70px;
background-color: transparent;
}
}

#cd-logo {
float: left;
margin: 13px 0 0 5%;
}
#cd-logo img {
display: block;
}
@media only screen and (min-width: 300px) {
#cd-logo {
margin: 23px 0 0 5%;
}
}

.cd-primary-nav {
/* mobile first - navigation hidden by default, triggered by tap/click on navigation icon */
float: right;
margin-right: 5%;
width: 44px;
height: 100%;
background: url("../assets/cd-icon-menu.svg") no-repeat center center;
}
.cd-primary-nav ul {
position: absolute;
top: 0;
left: 0;
width: 100%;
-webkit-transform: translateY(-100%);
-moz-transform: translateY(-100%);
-ms-transform: translateY(-100%);
-o-transform: translateY(-100%);
transform: translateY(-100%);
}
.cd-primary-nav ul.is-visible {
box-shadow: 0 3px 8px rgba(0, 0, 0, 0.2);
-webkit-transform: translateY(50px);
-moz-transform: translateY(50px);
-ms-transform: translateY(50px);
-o-transform: translateY(50px);
transform: translateY(50px);
}
.cd-primary-nav a {
display: block;
height: 50px;
line-height: 50px;
padding-left: 5%;
background: #21272c;
border-top: 1px solid #333c44;
color: #ffffff;
}
@media only screen and (min-width: 768px) {
.cd-primary-nav {
/* reset navigation values */
width: auto;
height: auto;
background: none;
}
.cd-primary-nav ul {
position: static;
width: auto;
-webkit-transform: translateY(0);
-moz-transform: translateY(0);
-ms-transform: translateY(0);
-o-transform: translateY(0);
transform: translateY(0);
line-height: 70px;
}
.cd-primary-nav ul.is-visible {
-webkit-transform: translateY(0);
-moz-transform: translateY(0);
-ms-transform: translateY(0);
-o-transform: translateY(0);
transform: translateY(0);
}
.cd-primary-nav li {
display: inline-block;
margin-left: 1em;
}
.cd-primary-nav a {
display: inline-block;
height: auto;
font-weight: 600;
line-height: normal;
background: transparent;
padding: .6em 1em;
border-top: none;
}
}

/* --------------------------------

Slider

-------------------------------- */
.cd-hero {
position: relative;
-webkit-font-smoothing: antialiased;
-moz-osx-font-smoothing: grayscale;
}

.cd-hero-slider {
position: relative;
height: 360px;
overflow: hidden;
}
.cd-hero-slider li {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
-webkit-transform: translateX(100%);
-moz-transform: translateX(100%);
-ms-transform: translateX(100%);
-o-transform: translateX(100%);
transform: translateX(100%);
}
.cd-hero-slider li.selected {
/* this is the visible slide */
position: relative;
-webkit-transform: translateX(0);
-moz-transform: translateX(0);
-ms-transform: translateX(0);
-o-transform: translateX(0);
transform: translateX(0);
}
.cd-hero-slider li.move-left {
/* slide hidden on the left */
-webkit-transform: translateX(-100%);
-moz-transform: translateX(-100%);
-ms-transform: translateX(-100%);
-o-transform: translateX(-100%);
transform: translateX(-100%);
}
.cd-hero-slider li.is-moving, .cd-hero-slider li.selected {
/* the is-moving class is assigned to the slide which is moving outside the viewport */
-webkit-transition: -webkit-transform 0.5s;
-moz-transition: -moz-transform 0.5s;
transition: transform 0.5s;
}
@media only screen and (min-width: 768px) {
.cd-hero-slider {
height: 500px;
}
}
@media only screen and (min-width: 1170px) {
.cd-hero-slider {
height: 680px;
}
}

/* --------------------------------

Single slide style

-------------------------------- */
.cd-hero-slider li {
background-position: center center;
background-size: cover;
background-repeat: no-repeat;
background-image: url(../assets/oneback2.jpg);
}
.cd-hero-slider li:first-of-type {
background-color: #2c343b;
}
.cd-hero-slider li:nth-of-type(2) {
background-color: #3d4952;
}
.cd-hero-slider li:nth-of-type(3) {
background-color: #5f2322;
}
.cd-hero-slider li:nth-of-type(4) {
background-color: #05132f;
}
.cd-hero-slider li:nth-of-type(5) {
background-color: #2c343b;
}
.cd-hero-slider .cd-full-width,
.cd-hero-slider .cd-half-width {
position: absolute;
width: 100%;
height: 100%;
z-index: 1;
left: 0;
top: 0;
/* this padding is used to align the text */
padding-top: 100px;
text-align: center;
/* Force Hardware Acceleration in WebKit */
-webkit-backface-visibility: hidden;
backface-visibility: hidden;
-webkit-transform: translateZ(0);
-moz-transform: translateZ(0);
-ms-transform: translateZ(0);
-o-transform: translateZ(0);
transform: translateZ(0);
}
.cd-hero-slider .cd-img-container {
/* hide image on mobile device */
display: none;
}
.cd-hero-slider .cd-img-container img {
position: inherit;
left: 100%;
top: 50%;
bottom: auto;
right: auto;
-webkit-transform: translateX(-50%) translateY(-50%);
-moz-transform: translateX(-50%) translateY(-50%);
-ms-transform: translateX(-50%) translateY(-50%);
-o-transform: translateX(-50%) translateY(-50%);
transform: translateX(-50%) translateY(-50%);
}
.cd-hero-slider .cd-bg-video-wrapper {
/* hide video on mobile device */
display: none;
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
overflow: hidden;
}
.cd-hero-slider .cd-bg-video-wrapper video {
/* you won't see this element in the html, but it will be injected using js */
display: block;
min-height: 100%;
min-width: 100%;
max-width: none;
height: auto;
width: auto;
position: absolute;
left: 50%;
top: 50%;
bottom: auto;
right: auto;
-webkit-transform: translateX(-50%) translateY(-50%);
-moz-transform: translateX(-50%) translateY(-50%);
-ms-transform: translateX(-50%) translateY(-50%);
-o-transform: translateX(-50%) translateY(-50%);
transform: translateX(-50%) translateY(-50%);
}
.cd-hero-slider h2, .cd-hero-slider p {
text-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
line-height: 1.2;
margin: 0 auto 14px;
color: #ffffff;
width: 90%;
max-width: 400px;
}
.cd-hero-slider h2 {
font-size: 2.4rem;
}
.cd-hero-slider p {
font-size: 1.4rem;
line-height: 1.4;
}
.cd-hero-slider .cd-btn {
display: inline-block;
padding: 1.2em 1.4em;
margin-top: .8em;
background-color: rgba(212, 68, 87, 0.9);
font-size: 1.3rem;
font-weight: 700;
letter-spacing: 1px;
color: #ffffff;
text-transform: uppercase;
box-shadow: 0 3px 6px rgba(0, 0, 0, 0.1);
-webkit-transition: background-color 0.2s;
-moz-transition: background-color 0.2s;
transition: background-color 0.2s;
}
.cd-hero-slider .cd-btn.secondary {
background-color: rgba(22, 26, 30, 0.8);
}
.cd-hero-slider .cd-btn:nth-of-type(2) {
margin-left: 1em;
}
.no-touch .cd-hero-slider .cd-btn:hover {
background-color: #d44457;
}
.no-touch .cd-hero-slider .cd-btn.secondary:hover {
background-color: #161a1e;
}
@media only screen and (min-width: 768px) {
.cd-hero-slider li:nth-of-type(2) {
background-image: none;
}
.cd-hero-slider li:nth-of-type(3) {
background-image: none;
}
.cd-hero-slider li:nth-of-type(4) {
background-image: none;
}
.cd-hero-slider .cd-full-width,
.cd-hero-slider .cd-half-width {
padding-top: 150px;
}
.cd-hero-slider .cd-bg-video-wrapper {
display: block;
}
.cd-hero-slider .cd-half-width {
width: 45%;
}
.cd-hero-slider .cd-half-width:first-of-type {
left: 5%;
}
.cd-hero-slider .cd-half-width:nth-of-type(2) {
right: 5%;
left: auto;
}
.cd-hero-slider .cd-img-container {
display: block;
}
.cd-hero-slider h2, .cd-hero-slider p {
max-width: 520px;
}
.cd-hero-slider h2 {
font-size: 2.4em;
font-weight: 300;
}
.cd-hero-slider .cd-btn {
font-size: 1.4rem;
}
}
@media only screen and (min-width: 1170px) {
.cd-hero-slider .cd-full-width,
.cd-hero-slider .cd-half-width {
padding-top: 220px;
}
.cd-hero-slider h2, .cd-hero-slider p {
margin-bottom: 20px;
}
.cd-hero-slider h2 {
font-size: 3.2em;
}
.cd-hero-slider p {
font-size: 1.6rem;
}
}

/* --------------------------------

Single slide animation

-------------------------------- */
@media only screen and (min-width: 768px) {
.cd-hero-slider .cd-half-width {
opacity: 0;
-webkit-transform: translateX(40px);
-moz-transform: translateX(40px);
-ms-transform: translateX(40px);
-o-transform: translateX(40px);
transform: translateX(40px);
}
.cd-hero-slider .move-left .cd-half-width {
-webkit-transform: translateX(-40px);
-moz-transform: translateX(-40px);
-ms-transform: translateX(-40px);
-o-transform: translateX(-40px);
transform: translateX(-40px);
}
.cd-hero-slider .selected .cd-half-width {
/* this is the visible slide */
opacity: 1;
-webkit-transform: translateX(0);
-moz-transform: translateX(0);
-ms-transform: translateX(0);
-o-transform: translateX(0);
transform: translateX(0);
}
.cd-hero-slider .is-moving .cd-half-width {
/* this is the slide moving outside the viewport
wait for the end of the transition on the <li> parent before set opacity to 0 and translate to 40px/-40px */
-webkit-transition: opacity 0s 0.5s, -webkit-transform 0s 0.5s;
-moz-transition: opacity 0s 0.5s, -moz-transform 0s 0.5s;
transition: opacity 0s 0.5s, transform 0s 0.5s;
}
.cd-hero-slider li.selected.from-left .cd-half-width:nth-of-type(2),
.cd-hero-slider li.selected.from-right .cd-half-width:first-of-type {
/* this is the selected slide - different animation if it's entering from left or right */
-webkit-transition: opacity 0.4s 0.2s, -webkit-transform 0.5s 0.2s;
-moz-transition: opacity 0.4s 0.2s, -moz-transform 0.5s 0.2s;
transition: opacity 0.4s 0.2s, transform 0.5s 0.2s;
}
.cd-hero-slider li.selected.from-left .cd-half-width:first-of-type,
.cd-hero-slider li.selected.from-right .cd-half-width:nth-of-type(2) {
/* this is the selected slide - different animation if it's entering from left or right */
-webkit-transition: opacity 0.4s 0.4s, -webkit-transform 0.5s 0.4s;
-moz-transition: opacity 0.4s 0.4s, -moz-transform 0.5s 0.4s;
transition: opacity 0.4s 0.4s, transform 0.5s 0.4s;
}
.cd-hero-slider .cd-full-width h2,
.cd-hero-slider .cd-full-width p,
.cd-hero-slider .cd-full-width .cd-btn {
opacity: 0;
-webkit-transform: translateX(100px);
-moz-transform: translateX(100px);
-ms-transform: translateX(100px);
-o-transform: translateX(100px);
transform: translateX(100px);
}
.cd-hero-slider .move-left .cd-full-width h2,
.cd-hero-slider .move-left .cd-full-width p,
.cd-hero-slider .move-left .cd-full-width .cd-btn {
opacity: 0;
-webkit-transform: translateX(-100px);
-moz-transform: translateX(-100px);
-ms-transform: translateX(-100px);
-o-transform: translateX(-100px);
transform: translateX(-100px);
}
.cd-hero-slider .selected .cd-full-width h2,
.cd-hero-slider .selected .cd-full-width p,
.cd-hero-slider .selected .cd-full-width .cd-btn {
/* this is the visible slide */
opacity: 1;
-webkit-transform: translateX(0);
-moz-transform: translateX(0);
-ms-transform: translateX(0);
-o-transform: translateX(0);
transform: translateX(0);
}
.cd-hero-slider li.is-moving .cd-full-width h2,
.cd-hero-slider li.is-moving .cd-full-width p,
.cd-hero-slider li.is-moving .cd-full-width .cd-btn {
/* this is the slide moving outside the viewport
wait for the end of the transition on the li parent before set opacity to 0 and translate to 100px/-100px */
-webkit-transition: opacity 0s 0.5s, -webkit-transform 0s 0.5s;
-moz-transition: opacity 0s 0.5s, -moz-transform 0s 0.5s;
transition: opacity 0s 0.5s, transform 0s 0.5s;
}
.cd-hero-slider li.selected h2 {
-webkit-transition: opacity 0.4s 0.2s, -webkit-transform 0.5s 0.2s;
-moz-transition: opacity 0.4s 0.2s, -moz-transform 0.5s 0.2s;
transition: opacity 0.4s 0.2s, transform 0.5s 0.2s;
}
.cd-hero-slider li.selected p {
-webkit-transition: opacity 0.4s 0.3s, -webkit-transform 0.5s 0.3s;
-moz-transition: opacity 0.4s 0.3s, -moz-transform 0.5s 0.3s;
transition: opacity 0.4s 0.3s, transform 0.5s 0.3s;
}
.cd-hero-slider li.selected .cd-btn {
-webkit-transition: opacity 0.4s 0.4s, -webkit-transform 0.5s 0.4s, background-color 0.2s 0s;
-moz-transition: opacity 0.4s 0.4s, -moz-transform 0.5s 0.4s, background-color 0.2s 0s;
transition: opacity 0.4s 0.4s, transform 0.5s 0.4s, background-color 0.2s 0s;
}
}
/* --------------------------------

Slider navigation

-------------------------------- */
.cd-slider-nav {
position: absolute;
width: 100%;
bottom: 0;
z-index: 2;
text-align: center;
height: 55px;
background-color: rgba(0, 1, 1, 0.5);
}
.cd-slider-nav nav, .cd-slider-nav ul, .cd-slider-nav li, .cd-slider-nav a {
height: 100%;
}
.cd-slider-nav nav {
display: inline-block;
position: relative;
}
.cd-slider-nav .cd-marker {
position: absolute;
bottom: 0;
left: 0;
width: 60px;
height: 100%;
color: #d44457;
background-color: #ffffff;
box-shadow: inset 0 2px 0 currentColor;
-webkit-transition: -webkit-transform 0.2s, box-shadow 0.2s;
-moz-transition: -moz-transform 0.2s, box-shadow 0.2s;
transition: transform 0.2s, box-shadow 0.2s;
}
.cd-slider-nav .cd-marker.item-2 {
-webkit-transform: translateX(100%);
-moz-transform: translateX(100%);
-ms-transform: translateX(100%);
-o-transform: translateX(100%);
transform: translateX(100%);
}
.cd-slider-nav .cd-marker.item-3 {
-webkit-transform: translateX(200%);
-moz-transform: translateX(200%);
-ms-transform: translateX(200%);
-o-transform: translateX(200%);
transform: translateX(200%);
}
.cd-slider-nav .cd-marker.item-4 {
-webkit-transform: translateX(300%);
-moz-transform: translateX(300%);
-ms-transform: translateX(300%);
-o-transform: translateX(300%);
transform: translateX(300%);
}
.cd-slider-nav .cd-marker.item-5 {
-webkit-transform: translateX(400%);
-moz-transform: translateX(400%);
-ms-transform: translateX(400%);
-o-transform: translateX(400%);
transform: translateX(400%);
}
.cd-slider-nav ul::after {
clear: both;
content: "";
display: table;
}
.cd-slider-nav li {
display: inline-block;
width: 60px;
float: left;
}
.cd-slider-nav li.selected a {
color: #2c343b;
}
.no-touch .cd-slider-nav li.selected a:hover {
background-color: transparent;
}
.cd-slider-nav a {
display: block;
position: relative;
padding-top: 35px;
font-size: 1rem;
font-weight: 700;
color: #a8b4be;
-webkit-transition: background-color 0.2s;
-moz-transition: background-color 0.2s;
transition: background-color 0.2s;
}
.cd-slider-nav a::before {
content: '';
position: absolute;
width: 24px;
height: 24px;
top: 8px;
left: 50%;
right: auto;
-webkit-transform: translateX(-50%);
-moz-transform: translateX(-50%);
-ms-transform: translateX(-50%);
-o-transform: translateX(-50%);
transform: translateX(-50%);
background: url(../assets/cd-icon-navigation.svg) no-repeat 0 0;
}
.no-touch .cd-slider-nav a:hover {
background-color: rgba(0, 1, 1, 0.5);
}
.cd-slider-nav li:first-of-type a::before {
background-position: 0 0;
}
.cd-slider-nav li.selected:first-of-type a::before {
background-position: 0 -24px;
}
.cd-slider-nav li:nth-of-type(2) a::before {
background-position: -24px 0;
}
.cd-slider-nav li.selected:nth-of-type(2) a::before {
background-position: -24px -24px;
}
.cd-slider-nav li:nth-of-type(3) a::before {
background-position: -48px 0;
}
.cd-slider-nav li.selected:nth-of-type(3) a::before {
background-position: -48px -24px;
}
.cd-slider-nav li:nth-of-type(4) a::before {
background-position: -72px 0;
}
.cd-slider-nav li.selected:nth-of-type(4) a::before {
background-position: -72px -24px;
}
.cd-slider-nav li:nth-of-type(5) a::before {
background-position: -96px 0;
}
.cd-slider-nav li.selected:nth-of-type(5) a::before {
background-position: -96px -24px;
}
@media only screen and (min-width: 768px) {
.cd-slider-nav {
height: 80px;
}
.cd-slider-nav .cd-marker,
.cd-slider-nav li {
width: 95px;
}
.cd-slider-nav a {
padding-top: 48px;
font-size: 1.1rem;
text-transform: uppercase;
}
.cd-slider-nav a::before {
top: 18px;
}
}

/* --------------------------------

Main content

-------------------------------- */
.cd-main-content {
width: 90%;
max-width: 768px;
margin: 0 auto;
padding: 2em 0;
}
.cd-main-content p {
font-size: 1.4rem;
line-height: 1.8;
color: #999999;
margin: 2em 0;
}
@media only screen and (min-width: 1170px) {
.cd-main-content {
padding: 3em 0;
}
.cd-main-content p {
font-size: 1.6rem;
}
}

/* --------------------------------

Javascript disabled

-------------------------------- */
.no-js .cd-hero-slider li {
display: none;
}
.no-js .cd-hero-slider li.selected {
display: block;
}

.no-js .cd-slider-nav {
display: none;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<section class="cd-hero">
<ul class="cd-hero-slider autoplay">

<li class="selected">
<div class="cd-half-width cd-img-container">
<img src="https://placeholdit.imgix.net/~text?txtsize=83&txt=1000%C3%97780&w=1000&h=780" alt="tech 1">
</div> <!-- .cd-full-width -->
</li>

<li>
<div class="cd-half-width cd-img-container">
<img src="http://lorempixel.com/1000/780/sports" alt="tech 1">
</div> <!-- .cd-half-width.cd-img-container -->
</li>

</ul> <!-- .cd-hero-slider -->

</section> <!-- .cd-hero -->




Answer

Here's a quick solution to your issue (please see the below fiddle for complete integration):

var sectionContainer = $('.cd-hero');
var slideColors = ['red', 'blue'];

function updateBackgroundColor(currentSlideIndex) {
    if(currentSlideIndex < slideColors.length) {
        sectionContainer.css('background-color', slideColors[currentSlideIndex]);
    }
}

And then calling updateBackgroundColor in the nextSlide and prevSlide methods with the n (index) argument should do the trick.

The array slideColors can be added to and the positions in the array will correlate to their respective image positions in your carousel.

In action:

https://jsfiddle.net/12dd5j1s/2/

Note: the initial background-color was set via css