when they do FFFF00, break it into FF FF 00, then convert the hexidecimal into decimal (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F -> 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
and you'll get 15 15 15 15 0 0
multiply the first number (15 15) by 16 to get 240, add the 2nd number (15 15) to get 255
then divide that by 255 to get the numerical equivalent
F0AF05 -> 240 175 5 -> 0.94 0.69 0.20 (rounded)