Sorry but you'll have to wait till I have time to rig up a WS2803 with some LEDs to figure out what's going on. My first guess would be the code, but I'm not familiar with adafruit's code, so I don't know. However, what I do know is that the standard WS2801 code won't work for the WS2803 because it has 6x more bits that needs to be sent. But as I said, I don't know adafruit's code, so it's possible they're already accounting for that. Also, try putting your LED's ground pins to outputs 0, 1, and 2 instead of starting at output 8. The other side goes to VCC. Make sure you're using the proper sides on the LED.