1999 XLT 4x4 with 4.0L OHV. Bought recently.

Coolant reservoir says “Gold fill” on the outside. I thought the original coolant was green.

Does this mean someone converted to gold coolant and took the effort to swap to a reservoir intended for gold?

 

How many miles are on your "NTY" Ranger?

Back when G-05 -a real common formulation- was introduced, many referred to it as "Mercedes-Benz Gold" (say it with a whispering tone suggestive of awe).
Is your "Gold fill" marked reservoir a Ford part with the "Gold fill" cast into the plastic or is it just an applique'?
Cashing in on the 'gold mystique' is what you're seeing.
Didn't Ford call their G-05 "Ford Gold" too?

Using G-05 is all you need to do.

 

160k miles. I don’t know if it’s a Ford part but “Gold fill” is cast into the plastic.

I did conclude that G05 is what I need to top off and eventually replace. Currently it has a clear yellowish coolant but was curious whether people actually swap out the reservoir.

 

"...curious whether people actually swap out the reservoir."
Maybe reservoirs older than yours (pre-'99) had nothing embossed?
I wouldn't think a message worded, "Use Green Coolant" was ever used.

Seriously, ask that question in the "General Ford Ranger Discussion" section.
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Oh I’m stupid.

Upon closer inspection it says “Cold fill” not “Gold fill”!!! In my defense the embossing is hard to see with the airbox in the way, and it’s a dirty 26 yo engine bay, and my brain was focused on coolant color!

Still, the PO had yellow or gold coolant, so I’ll stick to the G05 which I understand to be a safe option in this case.

 

Hey, if I had a nickel for every time I misread something....I'd have a lot of nickels!