1967 Quarter.different Planchet, Red Coloring?

Copper takes on many different colors, depending on the environment it has lived in and to any type of chemicals it was exposed to.That will explain the different color of the edges. As for the obverse toning? anybody's guess.
My first guess would be that the cladding was worn down to expose the copper core? Although I'm not seeing wear on the devices to account for that much wear.
Another could be a thin cladding in that area, or,
just simply a stain on the coin

The cladding is 75% copper and 25% nickel. On these, I think two things are possible, depending on conditions. Both are post mint damage.

One, the nickel is leached out in a corrosive environment. The process is called denickelification in corrosion science and is well documented. The general phenomenon is called dealloying, and is sometimes done intentionally.

The other possibility is that oxidized copper in the form of soluble copper ions plate over the cladding as part of the reduction half reaction while something else is corroding.

I have actually made the latter happen using corrosion products collected from coins and some common household chemicals used in food.

Environmental damage.