I've used a product called Picture This by Plaid. You need to color copy
the artwork, photo or whatever and follow the directions on the bottle. I can
tell you more about the process if you want.
The other idea is to get them to use fabric crayons found in the fabric
dept. They would color with those onto paper shaped like a tie (I would go
bigger) and then iron it onto the tie. Both of these methods will be in