This is a good use of a sample PIC chip and a handful of extra components. Check out the site for a complete schematic and construction details.

“On this page i will explain how i created my own colour changing lamp with red, green and blue leds that fades between all colours of the rainbow. It really comes out well at night when other light are dimmed. In daylight conditions the colors aren’t noticed well. Although it’s low budget i must say the result is nice. Here are some photo’s of my lamp in action. Click on any foto to see it in a bigger size.

So if it’s low budget, what did you use? Well, mainly free stuff lying around. For the casing i used a plastic pyramid of ferrero rocher chocolates. I also used a microchip pic16f628 microprocessor i got from a free sample. Then i used some resistors and transistors i soldered out from old electronics. The LEDS were the most expensive. I used extra bright ones (red: 3000 mcd, green: 4000 mcd, blue:5000 mcd, all with a 25 degrees opening). I also purchased a battery holder for 4 AAA batteries which power this lamp for 10 hours non stop light effects.”

Via: Make