DeviantArt member Laovaan creates all kinds of beautifully shaded watercolors. In this video he fields viewer questions as he spends five hours creating a watercolor of Link from The Legend of Zelda.
Some of the more vibrant colors are created using Colorex inks instead of traditional watercolors, but they are applied using the same technique. It's interesting to watch how often he wets the paper and reworks an area to give it that smooth gradient. Very relaxing to have on in the background while multitasking.
Bonus video: With Her Strength: