I got 23.<p>I know I'm a typical "partially color blind" male, e.g. I always fail those tests where they show you an image made of a bunch of colored dots and ask what number you see, but on this test, I found I could find the outlier much more easily by using my peripheral vision: staring directly at it the grid, all the squares would look the same, but by looking to the side and sort of scanning with the edge of my vision, one would suddenly jump out...