http://meta.wikipedia.org/wiki/The_polygon_map
Political maps use 2-level coloring schemes. Main color is selected as to avoid 2 neighbour countries having the same color. It's shade is selected randomly.
The problem is to select such N (N about 8) colors generators, and such colors for seas, rivers, city and country labels, and other objects (borders, river/mountains/island/sea labels etc.), that makes maps most readable.
Currently used scheme is:
Colors for: city dots white city labels white rivers #000060 seas #000060 country labels #FF8080 Color generator 0 # cyan $r = rand 64; $g = 160 + rand 64; $b = 160 + rand 64; Color generator 1 # green $r = 64 + rand 64; $g = 160 + rand 64; $b = 64 + rand 64; Color generator 2 # yellow-green $r = 128 + rand 32; $g = 192 + rand 64; $b = rand 32; Color generator 3 # greenish-blue $r = rand 32; $g = 64 + rand 64; $b = 128 + rand 64; Color generator 4 # yellow $r = 128 + rand 64; $g = 96 + rand 64; $b = rand 32; Color generator 5 # orange $r = 128 + rand 64; $g = 64 + rand 64; $b = rand 64; Color generator 6 # magenta $r = 160 + rand 64; $g = 64 + rand 64; $b = 160 + rand 64; Color generator 7 # gray $r = 96 + rand 64; $g = $r - 16 + rand 32; $b = $r - 16 + rand 32;
But it doesn't give very good results.
Anyone with better idea for coloring ?