15 Using `l3color` one can get this data directly. At present, the colours are independent of those from `xcolor`, so will have to be defined
14 You could calculate it manually. An html colour follows the structure #RRGGBB (in base 16) and colour mixing is normally a linear interpolation. So in your case, your colour has a red value of 12~16~ (= 18~10~), a green value of 34~16~ (= 52~10~) and a blue value of 56~16~ (= 86~10~). Thus the colour components after mixing are:
7 The usual advice in presenting quantitative information is to keep the information/ink ratio as good as possible. Amongst other things, this means that repetitive information should be avoided if possible.