Adjusting by Eye with Variations
The most obvious way to make a color adjustment is to compare before and after views of an image. In Photoshop, the tool for doing this is called Variations. It's the last item on the Image→Adjustments submenu. Variations combines several image adjustment tools into one easy-to-use system that shows you thumbnail images that are variations on the original image. You simply click the one that looks best to you. You can choose variations of hue and brightness and then see the result (which Photoshop calls Current Pick) compared to the original.
If Variations doesn't appear on the Adjustments submenu, ...