That's a good call. I know, back in the day, they mainly used PollyScale and Floquil military and railroad paints. I know from working on my Mandalorian armor that... Nnngg...
One of the yellows -- it was either Reefer Yellow or UP Armor Yellow -- that was used on ESB Boba is so close to the color of actual zinc chromate aviation primer that I can't see
any difference side by side. Caboose is the brighter red used on Boba's helmet -- I want to see how that looks as the squadron markings for Red Group.

You've also given me an idea for seeing how Insignia Yellow looks on a zinc chromate background, and what I might do to better isolate the former as squadron markings.
Reason I'm speculating on zinc chromate as a base color, apart from it being a real-world aviation primer, is it's the base color of Red Leader's helmet. Since the ANH helmets got reused in the subsequent films, I treat the markings as unit markings, like this:
View attachment 1433211
View attachment 1433212
...vis-a-vis their planes...
View attachment 1433213
So for one of my big projects, I'm turning my goofy-scale* 2002 Hasbro POTF2 Red Five (the first version of the big X-Wing they did) into a conjectural Rarified Air Cavalry late-model Z-95, inspired by Red Leader's helmet.
[*
The Kenner/Hasbro action figures are 1:18 scale. The vehicles have always been underscaled, but several times over the years they've tried to get at least closer to proportional. This X-Wing, though, is closer to Studio Scale -- 1:24 -- with the engines more like 1:30. So rather than dump time, money, and elbow grease into trying to correct all that to make it either accurately 1:18 or 1:24, I'm using it as a base to make a 1:18 late-model Z-95 -- where INCOM first rolled out the sort of S-foils that would get used on the T-65. I have a lot more freedom this way.]
Probably something like the centennial markings for the Red Devils:
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I've wibbled over all-over paintjobs, like on Anakin's Y-Wing in Clone Wars. It's space. They obviously don't care about camouflage, or they'd paint their fighters matte midnight blue. There are only so many naturally-occurring chemical elements. Most past the mid-90s (so far) are lab-created and break down to lighter elements pretty quickly. So presuming alloys or composites of elements we know many of the properties of... Zinc chromate (yellow or green) protects titanium, aluminum, and steel. The only light-gray metal primers I've run across are rust-inhibitors, which means iron-containing materials, and all of them terrestrial, rather than aviation.
So if the gray on the X-Wing or
Millennium Falcon or TIE Fighter isn't a bare primer layer, why paint a small spacecraft in a light, light-reflective shade like that? Is it for something like why NASA uses their white coatings -- for thermal regulation? Don't they have advanced enough systems in the GFFA that they don't need such basic tech? Or would it be a matter of "Hey, it works -- why not?"
So I get down to the question of: Are the yellow panels on these various X-Wings N.O.S., unused, with only a chromate-like primer coating on them? Or are they scavenged from a couple downchecked craft that had an all-over-yellow paint job, over the light-gray thermocoat? Or is the gray an aesthetically-relevant basecoat color, for reasons, and would that make yellow a similarly-relevant basecoat layer?
If the yellow was more chromate-like, I'd consider making those RAC X-Wings. But, as you point out, it's closer to Insignia Yellow. So, if I do an all-over-yellow basecoat, maybe it'd work for the Tierfon Yellow Aces:
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I've already put together a partmap of where the yellow panels on the Red Group fighters are located (never mind duplicates) to see where I have left over for those potential red markings. I'll scan it and see what your ideas are.