Maybe my post was confusing... Cutting a hole and making the edges smooth isn't a problem, the containers are clear though. I colored them with black sharpie. I haven't put them in with my snake yet because I didn't know if the sharpie smell would be harmful.
If drawing with a sharpie for a long time irritates my nose then I am sure it would be irritating to a snake that can smell a million times better than I can.