ors equally distant
 in the color space according to the Euclidean metric are equally distant
 perceptually). The L,u,v channels correspond roughly to luminance,
 green-red, blue-yellow. For more information see:
   http://en.wikipedia.org/wiki/CIELUV - using this color spaces
   http://en.wikipedia.org/wiki/CIELAB - more info about color spaces
 The LUV channels are normalized to fall in ~[0,1]. Without normalization
 the ranges are L~[0,100], u~[-88,182], and v~[-134,105] (and typically
 u,v~[-100,100]). 