@Ego Eram ReputoHey, that's super helpful! It's not perfect, but it's close enough to where it can probably be manually tweaked to match close enough to what it's probably supposed to look like (For examples where I don't have a correct result layed out for me, of course)
I was willing to accept this as the best I would probably get, but I did come across one more thing while playing around with those blend setting. In fact, its so simple I'm surprised I didn't notice it before.
When a pure white color is using the overlay blend mode above the correct result texture I'm trying to replicate, it returns the correct result back to the yellow box that made it up (well, like 99% the same, a few negligible ticks off barely noticeable by the eye). I was very excited to learn this, as I figured I could just do the opposite to at the very least make the yellow box the right color and go from there, but... the problem is, I couldn't exactly figure out HOW to do the opposite of that. I played with blacks and grays and multiply and the such, but I can't quite get to get this result backwards.
I think managing to reverse the process to re-obtain one of the original assets that made it is a good start, as I already can theory craft how to apply the differences in the grey box if just the yellow box was the right color. But of course I could be missing something and this could mean nothing at all... which would definitely be a bummer. If anyone has any ideas, I would love to hear them! Of course though, I thank you two for the help you've given already a ton, it's already helped get this way closer than I had it before.
(Also since I failed to remember to mention it in this post, overlaying white over the correct brown texture reverts it back to the brown box as well, it seems to be a global constant across these and the few I didn't post)