This here is a female shell cracker, a.k.a red ear sunfish. I catch these all the time. The females tend to stay this sort of gray color while the males get a much darker green coloration along with the blue pearling. I find that they often school with bluegill, pumpkin seeds and green sunfish so hybridization is pretty common with this specie.
They are a great pet fish and have a very cichlid like personality/behavior. Also don't be surprised that she doesn't gain anymore color as the females will only white was over time. I would recommend getting atleast a 75g for a pair of em as they do grow upto 12+in. Theses here are a couple of pics I pulled from Google to show a max sized female and a near max sized male.
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