In our Subjective photo processing iPhone app (please buy it and rate it!), we have to manipulate color in all the classic ways (and a few others). For example, increase saturation. I was very dissatisfied with all the color models commonly used in graphics.
One candidate was some general space like the CIE diagram. But like many applications we have an RGB space that starts and ends in RGB, so a simple gamut is good. The classic one is a cylinder of some kind such as HSV :
|The two most common cone RGB spaces (from an excellent wikipedia article)|
The practical problems with these spaces for my purposes are 1) intermediate colors such as yellow are not along a line from two colors that make them (red and green), and 2) computationally getting to and from the RGB cube is not that simple.
I hired Dave Hart as a consultant (who with Grue DeBry has founded a cool company Limnu developing collaborative white boards) to help my find the right space. Dave really liked this barycentic space for the hue part. Turns out this hue space is often used in computer vision because it factors out illumination and is good for getting a crude albedo transform. Here's a figure with that space on the right from a paper draft Dave and I may submit someday:
The computation for getting to and from this space is awesomely simple (and KISS is good!!!):