I think this qualifies as a tutorial?http://method.ac/
A collection of a few SVG-based games that teach you about color + color theory, beziers, typography, kerning.
I would recommend the color and bezier ones; the former gives you a limited time to match the given color(s), the latter lets you draw bezier curves to trace predefined shapes (with rating for accuracy and how few nodes you used).
Depending on your level of experience, the typography ('shape') and kerning games may also be interesting. In my opinion the scoring metrics used there are less sound, but they still have educational value.
BTW, GIMP is just "GIMP" (as the anyone on the devteam will tell you, it is not "The GIMP". Think about how "The GIMP" sounds in a sentence: awkward.)