I saw a piece by Blood Wolf the other day (their drawing of Toxic), and I thought it was cool how they used a solid color to create highlights, as opposed to using it to tint the desired area. I thought I might take this one step further and use a solid color for shading, too.
. . .
...I'll admit, it's not great, but I don't think I'll be deleting it. This was just a fun experiment, and it turned out better than it could have, I believe.
Link
Noxid
coloured shading is a good technique to try and learn
http://www.deviantart.com/art/Coloured-Shading-Tutorial-How-to-pick-a-palette-343488733
http://www.deviantart.com/art/Shading-Colour-choice-Tutorial-326726130
it makes the result look much more interesting I think