I have a load of (scraps of) old black and white patterned papers and got to work with brightly coloured Sharpies. Some black & white mini-alpha stickers got the Sharpie treatment too:
Pretty good effect and easy to do. I only experimented on a couple of punctuation stickers because I will colour the exact letters required as and when I need them.
Looking back at the originals I decided to try with other black & white patterns ... but this time the background showed rather more of my poor colouring in skills! The papers on the left barely show the Sharpies' colours spilling over onto the black, but the paper on the right only works from a large distance with half-closed eyes!
It's just as well I was experimenting with scraps!
Other Master Forgers have been busy over at the Counterfeit Kit Challenge Blog today - check out their forgeries here :-D