I missed this the first time around but for those interested in more advanced designs I built my colour darkroom analyser around a TAOS IC and a Microchip PIC. In particular I used the TCS230 which is an RGB light to frequency converter, however they have other alternatives depending on your usage. The only nuisance is that to be accurate it needs a filter but for what I used it for it wasn't needed.
Thanks for the great link. I didn't even know that was out there.