What’s in my coolant?

I have 203k on my TJ and popped open my radiator cap today because I’m leaving for a roadtrip soon so wanted to make sure everything was ok. There’s some black oily residue in the coolant. I had my head replaced at 191k miles because of a valve seat issue and had the coolant replaced at the same time.

As soon as I think coolant + oil my mind immediately thinks blown head gasket. I think I’m being paranoid but someone else give me their opinion. Overflow tank doesn’t have this crap oil is nice and clean on the dipstick. Am I right in this is probably just leftover grease and grime when my mechanic replaced my head?

Honestly, it runs fine, doesn’t lose coolant, 205-210 even climbing hills when its 100+ outside. I’m leaving for my trip tomorrow and am busy with packing. Just going to drain and refill the radiator with distilled water and keep an eye on it. I popped it open tomorrow this morning and it looks completely normal just a bit dirty.

Me being paranoid I want to test it but I’m going to fight the urge, drain and refill, and try not to worry about it.