Around the end of last year I was commisioned to design the circuit for a color detecting device for a paint company. The circuit was based around a DSP running at 32MHz and 7 TAOS color sensors and 7 calibrated ceramic LED modules that were custom designed. To do it right, there isnt a PIC available thats even close to powerful enough. Massive amounts of data need to be processed to determine color, shade, hue, contrast, refelectivity, age fade etc etc. You also need to calibrate with Carbon Black otherwise data gets screwy over time. Unless you have access to propriatory information, you are going to struggle to build a nice device.

I did not program this device, just designed the circuit and did the 6 layer pcb layout. This thing was modelled in MATLAB for months before a schematic was even started. Your housing will determine amount of ambient light and thus interfere with your result.

Can you tell its a pain in the butt to do it right?