Good but I wish it was more challenging. I played a few times and so far my high score is 81, which is far above the scale they give. I see the difference in color pretty much immediately, its just a matter of how fast I can move my finger to the correct square, so the limiting factor is how fast can I react, not how fast I can see the color difference. I am red-green colorblind, so maybe its a bit easier for me since Im better at perceiving differences in shades than most people.
Born2Ball about !Dr.Hue - Test Your Vision, Kuku Kube Color Tiles