I've looked at the sling bags a lot, but they strike me as kind of fussy to use. I like to just reach down an pull out a lens, or camera or whatever, without all the adjusting the sling bags seem to require. I've tried them out in shops, but haven't actually used one in picture taking, however. So maybe I'm not giving them a fair shake.
Certainly, for biking, or serious hiking where you might stop, set up and work from the bag for a bit, then pack up and move, I think they would be a big improvement over small backpack type bags.
Regarding the color, I was looking at one in a shop that had some Lowepro reps visiting, and told one of them I'd buy it if they made it in a light color. He sort of just looked at me, and couldn't seem to understand why I'd want a camera bag in any color but black.
He did, however, point out the built-in rain cover that is light colored.