I personally use fingernail polish. I have heard of a lot of guys using model car paint as well. Depending on the sight, I may paint it with the included brush, a toothpick, or a q-tip. I usually use 2 coats of white followed by maybe 2 coats of a bright orange. That may need adjusted, depending on the color, brand, desired look, etc. Some guys cover it with a clear coat afterward. Both fingernail polish and model car paint are cheap and available in a wide variety of colors and matte or shiny effects. It just may require a little experimentation on your end.