If your white light source has a flat spectrum, then the violet paint wouldn't be any dimmer than any other color. The reason red or blue paint looks bright eno

If your white light source has a flat spectrum, then the violet paint wouldn't be any dimmer than any other color. The reason red or blue paint looks bright enough to see is because, as you said, they do reflect a range. So the violet paint could reflect the same bandwidth range as the traditional visible spectrum paints, and it would have the same power density. Unless you mean appearance, in which case, yeah, our eyes don't detect violet very well.