Mulitplexing RGB LEDS

Hey guys, I want to control a minium of 6 RGB LED's. Ive done a search and a few posts came up but i dint quite understand if the chips i were looking at were the ones i wanted or not. I was wondering if you could advise me on the correct chip to buy.

It must have 8 bit pwm or higher, and min 18 output (6 x 3). Cheers

Phill