Nice job. Kind of reminds me of this one which increases the number of squares with the odd-one out becoming more subtle as you progress further in the game, but I prefer your sliding mechanic better for this kind of game.

https://vectorization.eu/color-perception-test

Ooh this one is fun too! Though it doesn't get quite as hard as the slider one. Breezed through all 47 levels of this pretty easily while there were one or two impossible seeming ones in the slider.

To me this seems primarily like an aim test, not a color perception test