X-Rite's "Test Your Color IQ." I almost aced this, leaving room for you to beat my score. Not much room, but room. See how you do. As Colin says, it's not much fun, but it's revealing. I'll post my score tomorrow, after you've had a chance to take the test yourself if you're so inclined.
Mike (Thanks to Steve Weeks, who got it from Colin Jago at Auspicious Dragon)
Mike's score—damn those blue-greens!
If you didn't score as well as many of those who left comments, note that voluntary reporting of performance-based tests will skew toward those who did well...the colloquial term is "bragging."People reporting scores in double digits probably would score well on a test for something called "honesty."
Both Ctein and I noticed on this test that there are slight luminance variations between some of the tiles, which can tend to throw you off. I'm more sensitive to luminance than I am to chroma. I was aware of my uncertainty in the region in which I showed error.
I'm going to close the comments soon because we're getting too many, and it's a chore for me to approve and post large numbers of comments.