1 - nail polish in your most vivid or favorite color
2 - plastic model paint in your most vivid or favorite color
3 - Aftermarket sights like Trijicon or the night sights
4 - Check at your local best well supplied gun store as they also should have site paint available.
You may have to repaint them over the years but it works pretty well.
I am getting ready to paint the sights on my LCP as they are barely visible in black.
Let us know what you end up using.