JAileen, I think that's a smart observation. I do think I'm influenced by light in my dressing, although it's not so much that sun makes me need less colour as that the quality of light combined with temperatures makes me crave different versions of my best colours. I love reds and pinks in winter (these are my warm colours) and vivid blues in summer (with white).
Smittie and I live in northern cities about 2 hours apart.
In the north, the days are short. So even sunny days do not give us a lot of light. In winter it can be dark by 4:30 pm or even earlier on a stormy day.
Where Smittie and I live, we don't experience unremitting cloud -- it is not like the PNW. Throughout fall and winter, we do get lots of clear, bright sunny days with sharp reflections off the snow -- particularly in her city which is colder and has longer winters than mine. (I live on the lake and it moderates the temperatures and snowfall and gives me slightly more cloudy days, I think).
However, my city especially is built of grey limestone so with bare branches on trees, grey streets, grey buildings. On sunny days this does not bother me, but if we go through a cloudy or rainy stretch it can be depressing.
Truth is, though, I love colour in summer and winter alike! I adore my neutrals, don't get me wrong. Ink, navy, denim, black, grey, white -- these are the staples of my closet. But without pops of bright colour I start to feel very depressed in any season.