Each button randomly cycles through colors. When pressed, all other buttons take the color of the pressed button, which highlights white. When released the buttons briefly stay at the held color before beginning to cycle again.
The video quality is poor, due to a combination of my crummy camera and my crummy skills at using it. The buttons aren't quite as bright as they seem in the video, but any flickering you might see is definitely not noticeable in person.
Read all about it at upnotnorth.blogspot.com/
2010 update: that Blogspot page is long abandoned. For the latest on this and (mostly) other projects, check out my new site at upnotnorth.net.