Though iGame's free Eye Test probably doesn't have any merit in the world of optometry, it's a fun game that can be of use to designers looking to hone their skills with hues. The game tests people's abilities to distinguish between closely similar colors, beginning with almost comically simple puzzles (for someone with 20/20 vision) and expanding to almost impossible levels.
The test's premise is easy for anyone to understand: it presents users with an array of colored squares, and they have to click the one that doesn't match. It begins with just four squares and a clear outlier, but as one gains points, the grid expands and the difference between colors gets narrower. Rather than staring in veins for minutes straight, each level lasts for just fifteen seconds before users fail, forcing them to click the right color as quickly as they can.