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 ?