I've seen an interesting 256 color palette here:
http://kim.oyhus.no/Palette256.htmlI understand it! Here is the mechanism:
Red uses values 0,
42, 85,
127, 170,
212, 255.
Green uses values 0,
23, 46,
69, 92,
115, 139,
162, 185,
208, 231,
255Blue uses values 0,
51, 102,
153, 204,
255.
Depedencies for green:
Green uses regular values if red and blue use same sets (regular or bold).
Green uses bold values if red and blue use different sets.
Depedencies for blue:
Blue uses regular values if red and green use same sets.
Blue uses bold values if red and green use different sets.
This makes 7x6x6 or 7x12x3=252 values. Black, white, red and cyan are represented exactly.
Remaining values are filled by grays: 51, 102, 153, 204.