I bought two nice plastic buckets and melted them in half to make two 3.5" high 6" wide hides. The problem is, the buckets are white and rather thin, so they don't block out the light. Obviously I want hides that will be nice and dark for her, since she really loves her totally dark ceramic caves.

I've done some searching on the subject of paint for reptiles, but found nothing conclusive. I will NOT use tape for any reason, and I can't use permanent marker because they're toxic. What can I use to make those white plastic hides nice and dark?