I made this box to help our 2 year old learn his colors. You can do so many variations with this. I have made something similar for colors, letters, shapes, and numbers.
then I taped construction paper rectangles on.
Then I cut out the holes. Be really careful. Watch your fingers.
Because the paper was not glued down, I had to put tape going into the hole to hold the paper down.
Then wrote the colors on it with a Sharpie.
Leave one side open so you can dump the pieces out and start over.