This application note from Microchip demonstrates color mixing using the PIC12F1572 MCU (PDF!):
This application note demonstrates color mixing using the PIC12F1572 processor. The PIC12F1572 processor features three 16-bit pulse-width modulators (PWMs), among other peripherals. The 16-bit PWMs allow precise control over each RGB LED, allowing smooth transitions even at low-brightness/luminosity levels.