Sam Wollaston alluded to this in his review of CSI:NY, but I don't think anyone has fully explored how the CSI franchise uses colour to tone its various incarnations.
CSI (Vegas - original and best): neon, stark
CSI: Miami (2nd version): sunny, beach colours; even in the indoor shots, the palette is sunny in tone
CSI: NY (darkness falls): neutral palette, stoney greys and earthy browns, harsh white interiors
In the crossover episode from Miami to NY (Case 63: MIA/NYC Non-Stop), this was even more starkly illustrated. Horatio Caine lit as if bringing the light of Florida to the cityscape; Mac Taylor - so obviously touched by the stark emotions of 9/11 - bleached into grey footage. (The contrast was so great at one point I considered if the cinematographers had adopted colouration of Caine as a focal point: anyone know if this is true?)