I've been using White Out on the front sight of my Springfield 1911A1 Loaded for over a year. I need the contrast...
The good thing about White Out is that it's bright, but it's only as permanent as you want it to be. You can always remove it, re-apply it, modify it, whatever you want... It sort of dries without ever completely drying; what I mean is, it dries enough to adhere to the sight but always seems to retain a degree of moisture that lets you easily remove it so that you can re-apply a fresh coat at a later date without having to resort to a file or sandpaper.
It's a poor man's way of making a modification to his gun, but it works for me.