I put 2 orange dots on the ball, one on either side of the number so that's actually 4 orange dots per ball.
This happened to me years ago ...
Playing a Titleist Pro V1 #2 marked as previously described and my tee shot found the middle of the fairway. My foursome walked to our balls and we found 5 balls in the fairway and two of them were exactly marked as previously described. A stranger on the adjacent fairway had sliced his ball onto my fairway and he was playing one of my lost balls, a ball he had found on some other day. Both balls were in the middle of my fairway so I told him to play which ever ball gave him the best chance to get through / over the trees to get back on his own fairway and I'd play on with the other.
I think there's a rule that states (approx) if you can't identify your ball then the ball is considered lost. If that's true then both balls would be considered lost. But my ball is marked, my ball is not lost. It's right here but according to the rules it is lost. Like the pro's we mark our balls uniquely to avoid situations like this but a pro would never put a marked ball in play that he found in the rough so I guess the real question is "How often do you CHANGE the mark on your ball?"