I think colourising coins is like the opposite of lipstick on a pig.
It's... putting pigshit on a pearl. :D
I have one guilty-pleasure exception and that's some Celtic coins I saw recently.. the colourisation was done by an artist, though. I think that's got slightly more merit as a collector's piece, but I would never stack multiples of those so it's separate issue really to bullion saving.
Sov