Screw waiting for tonight, I modified it now. It now will deselect if you click on the same box twice. Hope you enjoy.
Definitely helps. Thanks.
If you've got a few more bytes and a bit more time... A level transition would be good - even if it's just displaying the completed board and then going to the next level on a mouse click. (If you can fit in a "Next" button that would be even better).
And unless the instructions are meant to be cryptic and force us to figure things out, it would be convenient to list the primary colours and go into a lot more detail on rule 2. Otherwise I have to choose between just playing more-or-less at random or taking notes myself as I go along.
I don't want to come across as just a nit-picker, by the way. What you've done is pretty good for a week, and I understand that polish in 4k is hard. But the extra challenge of squeezing in as much polish as you can means extra pride in the achievement.