Can I just color the existing lens on my RealD glasses instead of new plastic?

[Prof. Layton]

I'm currently trying to get 3D on my PC, and since RealD doesn't work, I saw a tutorial saying to replace lens on some sunglasses with clear plastic, then coloring them, but I don't have any clear plastic. Can I just color the clear lens on my RealD glasses or do I need to buy completely new plastic?

[Juniez]

wouldn't that be really dark