Boards
Assign a colour to each number between 1 & 10.
A variation on the days of the week thing, but with numbers. More interesting I think. I've had a system since I was about 3.
1: Navy Blue
2: Dark Green
3: Light Green
4: Maroon
5: Yellow
6: Orange
7: Royal Blue
8: Pale Pink
9: Crimson
10. Black