decryption of rainbow encryption ( created by @abradbury ) WARNING! The code might eat up all your RAM

rainbow.py

import itertools
import binascii

# R - red
# O - orange
# Y - yellow
# G - green
# B - blue
# I - indigo
# V - violet
# W - white

# an array of all rainbox colours + white
LETTERS = ["R","O","Y","G","B","I","V","W"]
# string to decode
RAINBOW = "WOWWWWWRWYGWWVWWWGBWWWWYWBIWROWGWWVWWWWWWVRWYWWIWROYWWIVWWYWWWWWWYGWWWROWGBWVROYWBIWROYGWIVWOYWW"
# list of possible decodings
ENCODINGS = ["001","010","011","100","101","110","111","0"]
# list of lists of all permutations of encodings
PERMUTATIONS_OF_ENCODINGS = list(itertools.permutations(ENCODINGS))

# THE ALGORITHM
# iterate over each binary string of each permutation of encoding
# substitute each letter with the binary string
# convert the resulting binary string to ASCII

for bin_list in PERMUTATIONS_OF_ENCODINGS:
    for bin_string in bin_list:
    	t = RAINBOW
        for letter in LETTERS:
            t = t.replace( letter, bin_string)
        if len(t) % 8 == 0 :
            print ''.join(chr(int(t[i:i+8], 2)) for i in xrange(0, len(t), 8))