MacMahon Squares
I first saw these on the blog of Steve Natasiuk. http://mathonthemckenzie.blogspot.com/search?q=macmahon
The first question: given squares divided in four parts and three colors, how many are possible? (This sketch is a spoiler, but it's still a fun puzzle. Sort them to be sure you have them all.)
Then you can start to think like Percy MacMahon: what mathematical questions can you ask?
One classic is: can you make a rectangle where all the edges match color?
Percy liked to ask can you make one with all the same color on the outside edge?
Can you make 2 different rectangles at the same time using all the tiles with each rectangle with a constant color edge? Three rectangles?
A bit more about these at http://bit.ly/primesquares