Elimination of Dark Colored Cars to Save Fuel Is Like Spitting On a Forest Fire. Too Small to Matter.
What California (and the rest of the USA) needs is to get the goddamn gas-hog cars off the roads. Ban SUVs and huge pickups used for family cars. Ban "muscle cars". The USA should require a minimum mileage on all new cars of 30 MPG, certified by real drivers on real roads, not by running on a dynamometer. This policy would have a significant effect, but banning dark colors is so stupid that it is not worth consideration. One might as well ban bumper stickers.