Personally I like the glass up there. It is easier to keep clean than a painted surface. And I have noticed I get a lot of dead bugs up there. The glass you can scrub on hard and not risk scratches, whereas if it was painted you would have to be very careful scrubbing.

I would think a spray paint can from the inside would be pretty easy to do. If you only need to do it once every 10 years it seems like it is not worth making a huge project out of it.