That is a coffee and tea job, but the light caught the blades really odd to make it look like that. I was trying to avoid an all-black blade, so I coated the blades in Vicks Vapo-Rub to see if that would keep the coffee/tea stew from contacting them (I figured petroleum jelly would act as a water barrier). Some of it came off in the pan, probably due to temperature, so the blades ended up with a really random patina. I ran some 0000 steel wool over them, though, and they actually look pretty neat - very aged.
I'll try to remember to take a pic of the blades tomorrow in better light to demonstrate.
All of this was because after I saw the single blades and limited run of doubles in the darker bone, mine began to look too light, so I figured I'd 'speriment. Despite the Vicks fail, I am very pleased with the covers. They darkened up just the right amount for me. Previously, the lightest spots you see in the pic were almost white, and the overall tones just weren't as warm as they look now.