Hue is the color wheel. Once you know that a hue of 30 is orange, you immediately know that a hue of 30+180=210 is blue, since it's across from orange on the co

Hue is the color wheel. Once you know that a hue of 30 is orange, you immediately know that a hue of 30+180=210 is blue, since it's across from orange on the color wheel. How much time have you spent fiddling with RGB values to pick colors? I assume it's either a lot less or a lot more than me, because while I too can certainly imagine what any given mix would be, my imagination is usually so far off from the real result as to be useless. This has been true even when I worked in pure gray. 50% each of R, G, and B results in a perceptually very dark gray (that is, the contrast between #808080 and pure black, #000, is much less than the contrast between #808080 and pure white, #fff). Elsewhere in this thread I sang the praises of HCL, a color model where you can adjust independently the hue ("color" in the traditional sense, as in orange vs blue vs yellow vs green vs red), the perceived brightness, and the perceived "grayness" (saturation) of a color: http://vis4.net/blog/posts/avoid-equidistant-hsv-colors/ http://vis4.net/blog/posts/avoid-equidistant-hsv-colors/