Fast forward a couple of weeks. I'd gotten in a little board called the Stickduino. It's a small Arduino-compatible board that is about the size of a Flash drive. One end is a USB port, although it's not quite thick enough to make good contact in my laptop. I fix that with a couple of pieces of cardboard and a glue stick. I uploaded my arrows sketch to the board, then wired it up to the 1.3 RGB shield. The solid core wire was stiff enough to hold things in place, and it worked when I plugged it into my laptop.
To power this, I got out a $5 USB power supply I'd picked up on my California trip. It's not the most reliable gadget, but it's small, and if you aim the USB port to the ceiling, it will hold up the whole contraption. The picture is from it running in my bathroom. I've also got a YouTube video of it running it's very bright pattern below.
I'd probably not use this as a real nightlight, but as a quick light show at a party, I'm all over it. I also now have something to do with the rest of my v1.3 boards.