I actually tried something like this on my DMLE using mustard (French's Yellow). I applied the mustard to the de-greased blade, let it sit about an hour and repeted five times. The result was a nice mottled appearance. I was so happy with the results I plan to do a few others. I'll try and post pics tonight if time allows.

"And as the moon rises he sits by his fire, thinkin' about women and glasses of beer" JT