Painting the inside of the cluster a lighter color helps to brighten the cluster @ night as well.
I use something like white, or silver as a reflective paint. Chevy used a light green that I'm sure if you looked you could find some if keeping the car original is what you intend to do. I know some owners are super hard core in this area. Not that I blame them any. I would do the same with my 210 4-door Sedan.
Over the years, the clusters get handled over & over. The original paint can flake and fall off. With the inside surfaces now a dull reflective surface the dash lights don't seem to work as well.