I found a very cool little site that tests your ability to match a specific color based on hue, saturation and brightness. At first, I thought it was just kind of cute, but the more I played it, the more valuable I felt it was to improving your skills as a colorist. Trying to see and match colors is critical to a colorist. Also, as I played numerous iterations of the game, I realized that my eyes must have a specific deficiency in a hue range that is just on the magenta side of red. I was getting perfect and very good scores all the way around the color wheel, but in that specific area I was rarely getting very good scores.
Anyway, if you're looking to improve your ability to see and "dial in" specific colors, this is a great website. I've seen several other sites that are similar, but this is the best one, in my opinion.
The goal is that as each round starts, a circle of color in the center of the game starts to "clock wipe" to what ever color is under the cursor in the color wheel. The goal is to match the color on either side of the clock wipe. Each round is more challenging than the last as you begin trying to match multiple colors: complementary, tertiary and so on. It's a fun little game and very beneficial.
Book mark this baby and use your render time to good effect!