An old favourite
I took the bottom out and made a white canvas to fit in its place, then marked the squares through the tray. The seven columns on the right and the single column on the left were coloured variations on red. I then quietly filled in the remainder with suitable colours, and painted a shabby green frame to put around it. Even after the 15yrs that have passed since I made it, I find it very satisfying, I wish I still had it.
If you see it, let me know.