fun little game. I agree with other commenters that it would be great on mobile.
The timer is jank - a bug not a feature in my opinion. It seems to start or delay completely at random. I'd be ok if it didn't start until you pick the first square.
There's another issue where the current color changes as soon as the timer expires, which means if i'm clicking on color 1 when it switches to color 2, it registers as a failure. It would be nice if there were some grace period where it would just not register as points instead of being a failure.
Well done for the time limit!