Colors from 0-16777215. Where 0 is 0, 0, 0 and 16777215 is 255, 255, 255.

Position from 0-16777215. Where 0 is top left and 16777215 is bottom right.
For each prime number these two rules are applied. To use allRGB and give contrast to the prime numbers, all non prime numbers reverse the color: position 0 (0,0) is color 16777215 (255,255,255).