Blue seems to be a very popular alternative, but personally I find the default orange the easiest to read.
Still, it wouldn't kill the devs to offer some alternatives or colour sliders. It would be simplicity itself to put this in the config page.
I wouldn't mind being able to alter individual sections of the HUD, without having it totally banjax everything in the radar like the current method does.
Being able to change the default radar grid to green, for example, without losing the current target colors. I also wouldn't mind being able to change the other elements to different colors (blue panels for the Clipper!) separately from one another.
If they really want to get creative, they could even have a system similar to some MMORPGs (yes, I know ED isn't an RPG, that's not what I'm getting at) and have a UI menu that would allow folks to customize the HUD for each ship, if they want to.