Is it a good idea to spraypaint my axe head?
From my friend Kevin in a personal email:

You do not want to paint any striking or chopping part of an axe head.  Paint on the striking end will cause your axe to slip when hitting something.  Paint on the cutting end (from the edge all the way to the end of the wedge portion) will cause the axe to stick and bind into whatever you are cutting with every swing.