title: Color segmentation
body: <p>I need to segment the image by 7 colors (red, orange, yellow, green, light-blue, blue, violet) as in the rainbow. Do you know how to do it? Any papers or algorithms may be. For example it can be done by assigning each triple (r, g, b) a color. But it is not effective as we got there 255^3 of combinations.</p>