Paint for front sight bead.

i've used hot pink, lime green, and florescent orange fingernail polish on some front sights and it did fairly well...if painting the sight permanently though, it may be a good idea to dimple the bead (assuming the bead is metal) with a small punch to insure that whatever type of paint you choose stays put, but if you're really dead set on coloring the front sight, i'd skip the paint and buy a williams firesight to replace the factory bead.