Rice Boy by Evan Dahm is an epic webcomic, as is Tiny Kitten Teeth by Becky Dreistadt and Frank Gibson. Both use bright colors really well, particularly to emphasize the different moods of different locations/events/characters. (In Tiny Kitten teeth, I'm talking more about the storyline pages than the random single-panel paintings of Tigabuttah & co. You'll see what I mean if you follow the link :)
Examples after the jump.
Tiny Kitten Teeth:
The TKT ones are pretty overly busy, but I think that's pretty easily avoidable.