Statistically lighter cars have fewer crashes , but I dont think its enough to change insurance premiums. (I think they occasionally increase premium/insurance group for cars with fancy paint finishes that make repairs more expensive)
I too find dark colours harder to keep clean. Especially as I live in an area with very hard water. (kent)
That said I find my pearlescent white Jazz needs more work to keep clean than a plain white car I had a few years ago. I treated the Jazz with turtle wax hybrid ceramic spray which improved the water beading quite a lot, but it still needs more finishing off than the previous white car (which to be fair was in an area where the water was a bit softer. ) I probably need an improved shampoo. Anyone know one proven to work well in a Hard water area?