Just discovered a fantastic illustration duo, Zelda Devon and Kurt Huggins, who call their team Teetering Bulb (http://www.teeteringbulb.com/). I love the way they use not only color, but value, really well in their pieces. One of Zelda's blog posts says that it is important to "understand color values. Don't wade around in a grey soup. Grab screen stills from powerful black and white movies, like Hitchcock stills. Compare your work in grayscale. Is you work as powerful as a Hitchcock movie still?"
Some of their fabulous creations are below:
"Sometimes, you gotta draw it 6 or 7 times. Or 13 times."
"Astronauts and Dinosaurs!"
"Borrowed Dreams"
for Reader's Digest Asia
"You learn only by doing. Be fearless." -Zelda