An older thread but since there weren't many answer....
I've been painting my front sights for a long time. They work great.
First thoroughly clean the sight and tape off the edges.
Apply a white base paint, this is very important for the final look. I use an enamel paint pen with a fine point I got from a crafts store.
After the white has dried I put down a coat of Testors fluorescent orange (or color of your choice).
Let dry and peal the tape.
These aren't great pictures but they illustrate the difference.
Regular front sight:
Painted front sight: