Ok, here ya go......buy 4 tri colored led's, add the resistors, build a small PIC throw a potentiometer on it and there you go!
I am in the process of doing this now. This way you can have the tri colored led in each door handle as they slowly change from one color to several other colors, and you can still dim or brighten them! The leds would change in color similar to the pens that you can buy that when activated, they change colors through the shaft of the pen. They had them at the dollar store at one time.
I made a light refraction rod a while back (same principle)and installed it in my Cougar. It came on when I had my amp on so that I would remember to shut it off before I get out of the car. It worked very well!
