import Image, ImagePalette

im = Image.open('05_easter.gif')

p = im.palette

primes = (2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107,
          109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227,
          229, 233, 239, 241, 251)

p2 = []
for i in range(256):
    x = (255,255,255)
    if i in primes:
        x = (0x66,0,0)
    elif not i & 1:
        x = (0,0,0x66)

    p2.extend(x)

print p2

im.putpalette(p2)

im.save('answer.png')