How to have matlab identify a color

I need to identify 6 colors. These are red, orange, yellow, white, blue, and green. I do not know if there is a simple way to do this. The colors will be identified from an image, so they might have slight variations each time. The colors are R G B at the moment. My intial idea was to set parameters, for example red would be between 255 and 230. I am not sure how to set this up. And I dont know how I would corilated that value to being red in matlab.

any info helps, thanks.

[Walter Roberson]

Sometimes rgb2hsv() is used, with people associating color with the "hue" parameter.