"I would have grave reservations about working for any employer that would be sufficiently picky on this type of thing!"
Best not get a job in a regulated industry where this sort of thing is very important. It must drive "outsiders" bonkers to have these rules foisted upon them even if they are just consulting on site.
To address the original query if it were not specified I would tend to use black as it is IMO more legible however blue is a better ink to use from the perspective of a photocopy as the original is clearly distinguishable from the original.