There are over 300 wrenches out there with the MH imprint on them. Would they have been painted out of the fatory? Beats me. Most of mine are the fimailar "rust" color!!
I have seen them in variety of colors but my favorite is the take them down to the bare metal and just clearcoat them. This keeps the old look but makes for a fresh presentation. I have seen the older wrenches painted "Challenger" green and the newer ones painted MH red. Both have had the stamped MH and numbers highlighted with yellow.
If you could find a number on the wrench I could probably tell what equipment it was used with!
Just my opinion.