FWIW, note the rather "milky" appearance of the green and orange lite-brite pegs in your pic. These are the newer style, softer and more prone to discolor when heated. It's well worth trying to find an old lite-brite set, as the plastic was much better suited for this purpose ---ask me how I know...
Just a suggestion, but I bought a set of about 9 different see-thru colored handle toothbrushes from China online, and they were the better plastic type.
Ed