What are the HSV and HSL models?
HSV and HSL (or HLS) colorspaces are practical models which are not related to any specific material. They use the hue (H) system to code colors. To understand hue let imagine a circle where red is at position 0, green at position 120 and blue at 240. Obviously, by a rotation of another 120 step, you come back to red (because 360 points to the same position as 0). Now let imagine that between each of these points you do a progressive blend of the two adjacent colors. You observe a continuous transition between all possible colors (with yellow at 60, cyan – a sort of light blue – at 180, and magenta – a sort of purple – at 300). Saturation (the S component) is, roughly speaking, the inverse of the amount of white added to the color (that is when S = 100% no white is added to the color; for example pink is an unsaturated red). But the two models differ on the third component. V, for value, is a measure of the brightness of the color. For example a pure red 255 is H = 0, S = 100%, V = 100
