I have always been in favor of a dab of paint or nail polish on my front sight to help it jump out at me. As I got older I needed it more and more.
One of the best I had found was testors Acrylic Flourescent model paint. Today I found something even better and way easier to use.
I found this in the craft section of Walmart. They had bright green and hot pink. I have used the paint pens before on many projects but this is the first one I found that was like it was made for sights. It just goes on so easy.
Get a white one and lay down a base coat of white first to make the bright color on top really show. If you think you need it you can put a top coat of clear nail polish like "Hard as Nails" or some other nail polish protector.