I have blackened the rear dots and applied fluorescent enamel paint to all the front sights of my handguns (except the Night Guard, the XS Big Dot needed no "improvement"). I find the plain black rear sight and bright orange front works the best for me. Most all sights that are painted from the factory have the paint applied in dots or bars that have been indented or recessed, just fill'em up w/ a good durable enamel paint, let it cure for 24hrs in regular humidity and room temps and about 36hrs in high humidity or colder temps.
This also works with the white ring around tritium sights also, just paint the capsule and the white ring, wipe of the excess around the edges, let it dry for a couple hrs, even on the capsule, then take a straightened paper clip and gently remove the dried paint from the glass face of the capsule. Let the ring cure. (see above)
The glass is very slick so the paint that has been drying for approx: 2hrs, and is slightly tacky, comes off easily and precisely, leaving a crisp clear orange ring around the tritium vial. I've found this is the preferred method of removing paint from the capsule, as trying to remove it from the capsule w/ any modicum of precision, while still wet is near impossible. One then just has to black out the white rings round the rear tritiums and you're all set.
I use "Elmer's Painters" opaque paint markers pens w/ a medium tip (2.05mm tip) in Bright Orange. There is also a fluorescent yellow that is excellent under most lighting conditions. I find it kinda washes out in the bright midday sun but is much better in low light than the orange I use. The orange seems to be a good all around choice for me
Elmer's also has a fluorescent green that is very good, but I find it not very good at all in the Appalachian summertime w/ all it's greenery. In the wintertime it works very well against a backdrop of browns, tans and grays. It would perhaps be very good out West with it's more arid conditions year around. The orange seems to be a good all around choice for me and where I live.
While painted fluorescent enamel paints do take a back set to a well designed tritium set up or even to F.O. sights that have been properly designed for a good combo of visibility & durability (most F.O. sights sacrifice durability for visibility), painted sights are inexpensive, easily accomplished, durable and easily touched up if needed, though this is very rarely the case.
I painted the sights on a Walther P5, BHP and CZ75, USP9 and several revolvers well over 15yrs ago (closer to 20 now) and they are as good as the day I applied them.
Perhaps some here will find this useful, I hope it helps!