Photoshop :: Adjusting Color Backgrounds

Adjusting color backgrounds. I have a large number of images of fly-fishing flies which were photographed on not-quite-solid backgrounds of slightly differing colors. I'd like to efficiently adjust the backgrounds so they all appear roughly the same without affecting the flies themselves. The flies are hard to select because of their feathery, hair-like edges, and the backgrounds are hard to select because they have slight gradations of almost-solid colors.