Bleh - we need to get rid of CCD and CMOS and replace all 20 million pixels with photomultiplier tubes! Single photon counting is not a problem!

Ok, seriously though, I was unaware that the quantum efficiency of CCDs was >70%.

There is another way to sense color other than filters and the solar power folks are doing it now. Put your highest bandgap doping at the top of the stack, and reduce the gap for each progressively lower layer. Commercial solar power chips use 3 layers but there's no limit - so long as you're not absorbing the photons in the silicon crystal. This matches the energy of the photon to the absorption band of the semiconductor. For solar cells the result is more power, less heat. For cameras it would be a huge increase in range and also provide a better approximation of color - actually it could provide a low-res spectrum at each pixel.