Let your child choose and cut the color ribbons or yarn that he wants to use. I had different colors of ribbon already on hand. The length of the ribbon can also vary.
This is the part where I sneaked in a little learning for my 6 year old. We are still working with him on tying shoes and practicing over and over again isn't something he is really excited about doing. So tying the ribbons onto the kite helped him to practice the first part of tying over and over again. Make an X, loop it through, and pull it tight.