Rick, just go to Autozone, or any car parts store and pick up the widest mud flaps you can find. Usually for pickups.
I wouldn't suggest painting them. The best trick is to leave them black so they blend in with the tire.
Just make sure when you install them so that they are lined up with the tread of the tire, and don't stick out beyond the tires shoulder on the inside or the outside. (You can trim them if necessary) That way they are nearly invisible from behind.
Another thing is to hang them low enough to actually be functional.
Just take a wooden yardstick, and jam it under the tires tread, then pull the other end up to the bottom edge of the mud flap and you will see exactly where the mud, sand, and gravel is going to hit your rear bumper or your rocker panel.
Forum member Shibing "KURATSUNADE" installed them on his beautiful aero-blue coupe a couple years ago, and they really didn't look that bad.
Send him a PM and I'm sure he would post up some photo's of how it looked.
Good Luck