"all possible combinations of all 32-bit colours containing red index XX, green index XX, and blue index XX" six digits = 63 colours ( 2^7 - 1 ) 63 colours = 63! combinations (oops) a MASSIVE number. (19 zeroes) three digits ( colours like #444477, #447744, #774444 etc) 7 colours 5040 combinations + permutations ********* how about one red, one blue, and one green (colours like #000000, #4D0000, #00A200 .. .. #4DA276) ** isn't it 256 combinations? two digits (colours #DDD333, #333DDD, #333333, #DDDDDD) 4 colours (that was them) 24 combinations (see them all below) 00 01 10 11 00 01 11 10 00 10 01 11 00 10 11 01 00 11 01 10 00 11 10 01 01 10 11 00 . . 10 11 00 01 . . 11 00 01 10 . .