Select->Color Range, use the eye droppers to refine, and pray.
... But on second thought - why does this matter? Just buy Lightroom at the current introductory price (and of course QImage for printing).
Photoshop is passé.
= Obsolete.
= Out-moded.
If your image file can't be corrected using only global edits, either throw yourself in front of a freight train or sell your nubile offspring, then use the proceeds to upgrade to a more expensive capture system. And by all means always, always, always use a tripod, cable release, ND grads, handheld light meter, and of course carry prime lenses covering every focal length known to mankind with you at all times!