I started a sketchbook thread on conceptart.org, to get some critiques and find some new friends, and I realized that my painting skills  became rusty.
I work as a CG artist full time in game development and most of the time I work in 3D, I paint concept art or promotional material occasionally when it is needed. My skills were sufficient for what I had to do occasionally, but for the graphic novel that I have envisioned, it was just not enough.

So I started doing some painting exercises, taking real life photos and examining how color behave under different lighting conditions. Here is one of my studies.