So as apart of my 500 environment project, I'm doing a mastercopy every weekday. This week's artist was Dice Tsutsumi (www.simplestroke.com). I first saw his work in the Toy Story 3 artwork - really gorgeous use of color. He renders forms in a very solid fashion. Yet, his color and temperatures are very subtle. Love this guy's stuff. Will do more studies in the future.
I've been doing more color testing on paper recently. It helps me get more accurate and more harmonious color relationships.
I got some advice from my friend Jason (www.jasonscheier.com) to make each sketchbook page like a portfolio page. Basically - pay more attention to the composition on each page. So, I've been using the color tests as a composition element. Spending time to plan the composition in the beginning also saves me time when I'm uploading to my blog. I no longer have to crop, scale, move images to make it look more presentable. :)