I show APHA. I can tell you his color is very desirable in competition - except for the color classs. It is much less white to keep clean and the solid color doesn't draw attention to movement, black is a bonus as well. As other posters have noted his overo status on his papers is due to his white on his face - it is enough to qualify for the regular registry, which is why he has regular papers.
It is good that he is regular registry. You have many more options when showing than if he was a solid, more classes, more chances at high points and more competitors - so he is worth much more money than a solid paint would be.
Congrats on a very nice gelding, have fun with him.
There is no passion to be found playing small - in settling for a life that is less than the one you are capable of living. - Nelson Mandela