I'm trying to highlight a section of a Google Earth image that I brought into Photoshop CS6 using a transparent color. How can I do this?
Create a Selection (Selection Tool of choice), then, with that active, create an Adjustment Layer, say Hue, Brightness, Saturation, and that will be applied to the Selected area. Now, if you wish to maybe lighten, or darken the area outside that Selection, just hit Ctrl+Shift+I, to Invert the Selection, and apply that Adjustment Layer.
Good luck, and hope that helps,
Hunt