Change Revel BE driver color to black?

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

The weight of a berillium tweeter diagram is on the order of 5 to 10 miligrams. A mid-sized duck feather is 200 mg. Let’s spray a light coat of paint on that… what double the mass? I don’t know but it will be a non trivial weight change.

I would trade them in for equivalent or better speakers with black cones. Paint will change one or more characteristics of the cones, magic marker would likely look uneven (every time I tried coloring something with a marker it has looked terrible).