I wear a lot of black, and it's not because I'm depressed or anything. I like black jeans - they're pretty much the only colored jeans I wear. James Jeans have the most comfortable fabric. I'd say in general, I dress pretty comfortably.
Once, right before a show, I realized I'd forgotten shoes. I didn't want to wear my flip-flops onstage because I could trip. I ended up going barefoot, which actually worked out because it became my 'thing.'
I probably bring four dresses on the road and rotate those. I always wear something light when I go onstage because I move around a whole lot. It's a sweaty business.