Find the Odd Disk

Interesting. I only got 15/20, and previously considered myself "above average" at colour distinction tests but based on other replies that's not an especially good score. I'll try again, going more carefully.

Ah, yes, 19/20 the second time (only the last one wrong).

The first time I kept my eyes fixed in the same place roughly in the middle which clearly wasn't a good idea. On the second attempt I glanced between each circle in turn, trying to discern the difference over two points in time rather than two points in space.

I have poor color discrimination, but excellent flicker detection (?). This last skill was discovered by the senior devs when I was doing GPU driver debug, and “we” were looking for an extremely transient high-refresh rate tile clear issue. The issue only occurred at 120Hz (or higher) refresh rate with solid clear color on a large screen, with nearly identical colors. About one 4x8 pixel tile every minute or so. That was a boring few days, let me tell you.