cv::inRange(src, cv::Scalar(35, 20, 20), cv::Scalar(85, 255, 200), src);
Look at the HSV color wheel and pick the right range. Be aware that HSV has fit into 3 8 bit- channels, but the H channel does not, so you have to divide this value by 2. The range for H is 0-180 in OpenCV. See this question for reference.
With this configuration ( I tested the values with ImageJ not OpenCV)
cv::inRange(src, cv::Scalar(35, 60, 200), cv::Scalar(60, 255, 255), src);