Damn, did you see the mcd output on those displays? You couldn't light up the inside of a film canister... Anyway, if you're only looking to buy one 3-color LED, Mouser has them for about seven bucks a piece. They're either made by Chicago Miniature or Kingbright, I don't remember which. Either way, you're getting a VERY well made LED, with a minimum mcd output in the twenties, and an average in the seventies. By no means bright (your average "Super Bright" rated LED will output anywhere from 1000-3500 mcd) but more than visible. Anyway, until they make a Red/Blue bi-color, there is one other option. A low nM UV LED reverse biased with a red LED, both shining through the same LitePipe. Conveniently enough, Exabyte Systems sells a 400-405 nM UV LED in a five pack for $2.50 US available for order
here, and LitePipes are available from our friend Mouser for about twenty six cents a piece. All in all, you could make 5 Ghetto Rig Purple/Pick-a-Color LED's for about a buck a piece. Assuming you can wait for the parts to be mailed.
So yeah. I spend way to much time reading electronic supply catalogs.