Color Detection Algorithms

I am trying to write an algorithm for detection of the color green. The thing is that if I try detecting the shade of a pixel in a picture, there are more than a million different shades possible. How do I sift thourgh all these different shades and detect which ones are green ? Does anyone know of a simple way to do it or of any prevelant algorithms that does it for you ?

Just a thought, Get the pixel's rgb value. If the g > r && g > b then its a shade of green. Let me know what you come up with.