I'm pretty sure it's just colored plastic, but I've got a suggestion that might work for whatever you're doing.  I saw a project that someone did over at Xbox Scene, where he took the IR dongle that normally plugs into a controller port an permanently mounted it inside his Xbox, so that it would not take up a controller port.  Really cool.
Anyway, he drilled a small hole in the front of the xbox case to allow the IR light through, and he just covered it up with a piece of exposed film (I think he just taped it on from the inside).  It looked pretty good.  
I hope that's helpful.