Just an idea, but sometime ago I wrote some example code that showed how to vary the light output of an LED using the PIC18F8520's built-in PWM hardware. This code could be used with last year's IR beacon circuit to drive an array of tri-color high-brightness LEDs to create a pretty wide color spectrum. The filename is edu_led_pwm.zip and it's located here:
http://kevin.org/frc.
-Kevin