800 Scrambler - Mystery Plunger

I was trying to change the front drive sprocket but could not get it off with chain attached, so undid a black screw on a black plastic assembly (which had a plastic plunger shaft behind) and pulled it out to get more clearance.

Problem: Green oil stated running out the hole, (not engine oil I don’t think). I quickly refitted the plunger, but now am worried what the oil is from, or for or whatever.

Any clues what this is?

Could this be a Ducati chain oiler?

Any ideas greatly appreciated.

cepted and photo attached.