Whats wrong with this coin color its got like a smooth finish and the deterioration is it just circulation?
Hard to say where a 75 year old coin has been, so the color could be any number of things. The reverse looks like possibly struck through grease and a weak strike with a worn die. It would help if you photographed it on a white background and cropped better.
Looks like a cleaned coin (long ago) that was placed on a hot source, perhaps a cast iron stove, where it took on a bit of a blue/purple tint. I made a few of those as a kid...unfortunately.