So that's the reason John has black hair, huh? If I'm not wrong, black is the result of a ...

So that's the reason John has black hair, huh? If I'm not wrong, black is the result of a mix of all colour from pigment (paint) as seen in human eyes. So, is it actually hinting on his power?
The power of copying other people ability? Because if you mix every colour there is (we know that their hair colour is kinda showing their ability's colour), you'd get black. Though it's not yet confirmed what his power is. But, we pretty much have an inkling of what that is, no?