Yes, mostly heat.

 

So the black absorbs light energy (visible for the most part), so all that energy goes where, heat?

Yes.
But "all that energy" is very small.
If you were to put a piece of black velvet, which is a good light absorber, next to the device in normal ambient light, how warm to you think it would get?

 

Yes.
But "all that energy" is very small.
If you were to put a piece of black velvet, which is a good light absorber, next to the device in normal ambient light, how warm to you think it would get?

If you also had a similar piece of white velvet to compare, and good equipment, you probably could detect the difference.