Thread at ABSE (alt.binaries.schematics.electronic) caught my eye, pop over and read the full thread & get the code if interested. Note some revised code posted a couple of days ago.
You can buy RGB LED's with the IC built in to do this, with the standard 2 pins, which you connect to 5V.
Can you repost the code or a link to it here? The original message was gone from my news server by the time I saw this thread.