Change Revel BE driver color to black?

Wait for nighttime, then turn off the lights - plenty of black :)

Why would you want to do that?

Impossible, and a ridiculous idea!!!

Beryllium is an expensive, lightweight, very hard material that's great for tweeters.  I’d expect paint to add mass and change the sound, sort of defeating the purpose of choosing BE over other materials.  Don't do it.

I can’t image that would be possible without big effect on sound… negative.