I am extremely new to scikit-image (
rgb_image = imread("input_rgb_image.jpg")
rgb_image.shape # gives (1411L, 1411L, 3L)
green_image = rgb_image[:,:,1]
What you are extracting is just a single channel and this shows you how much green colour each pixel has. This will ultimately be visualized as a grayscale image where darker pixels denote that there isn't much "greenness" at those points and lighter pixels denote that there is a high amount of "greenness" at those points.
If I'm interpreting what you're saying properly, you wish visualize the "green" of each colour, then set both the red and blue channels to zero and leave the green channel intact.
rgb_image[:,:,0] = 0 rgb_image[:,:,2] = 0
However, if you just want to extract the green channel and visualize this as a grayscale image as I've mentioned above, then doing what you did above with the setting of your
green_image variable is just fine.