Pinouts usually use red and black to indicate power and ground [1]. It's possible to use several colours of solder mask on the same PCB. [2]

What I'd like to see is a developer board targeted at the education market that uses colours to show the traces.

I think that at least showing the power and ground could reduce the risk of shortouts. It would be a lot easier for teachers to say "plug the red wire into the red pin" instead of "the top right ... no, other top, turn it around".

[1] Raspberry Pi pinout https://cdn-images-1.medium.com/max/1000/1*QlSyHfcfNu4ePpNoN...

[2] https://i2.wp.com/makezine.com/wp-content/uploads/2009/12/20...