G'Day Richard, I painted mine with VHT Satin Black after first "etch priming" them to ensure that the paint would stick. I then cooked them in my kitchen oven (while the wie was out) to cure the paint. I went to my hardware store and bought some small "sample" cans of water based acrylic interior paint and a couple of model brushes and some cotton wool buds, and a saucer of water.
I then, very patiently, dribbled paint from the model brush into the impressed lettering on the switches, in the correct shade, using a cotton wool bud moistened in water (but not dripping) to quickly wipe off any excess. Once dry, it'll last as long as the original paint, and the advantage of a water based paint is that you don't need to use a chemical like thinners or turpentine to remove any excess, which might also damage the black paint. Cheers, Terry.
