CMY(K): cyan, magenta, yellow (black). These are the complements of red, green, blue, respectively. When used as filters they are called subtractive primaries and are commonly used in printing.
YIQ (similar to YUV): used in US commercial color-TV broadcasting. It is a recoding of rgb for transmission efficiency and for downward compatibility with black and white TV. The Y represents luminance (only this is shown on black and white TVs). The chromaticity is encoded in the I and Q. They are color differentials.
HSV (similar to HSB or HSL): hue, saturation, and value (or brightness). unlike the hardware oriented CMY, RGB, and YIQ, HSV is user oriented
HSV Model
CIE: see section below
For more details see Color Space FAQ
Ideally we want a way of graphically representing all colors. The problem with RGB is that some coefficients are negative and 3 dimensions are hard to view on a 2 dimensional page. To remedy this, CIE: XYZ "colors" were invented. That’s right, invented. They are not real colors in a physical sense. They are simply a linear transformations of the RGB values. This transformation was chosen so that matching functions can be represented by all positive coefficients. These coefficients are shown in the graph below:
To solve the 3D problem, we note that we can live without representing the luminance since this changes the intensity of the color but not the color itself. By normalizing x = X / (X+Y+Z) etc, we remove the luminance component. And since z = 1 - x - y is redundant we need not graph the z component. What we are left with is a CIE diagram which represent all possible visible colors in a 2D graph.
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