I wouldn't suggest clear.

Remember that our goal is providing an environment where they will feel secure and to maximize that effect you want to use something they cannot see through.

I use the ESU creature cubbies (they come in 3 different sizes and are black) and my gals all seem to like them.

If you like you can PM me and I'll send you one to check out. No obligation here - I don't sell supplies but I do appreciate your rescue effort.