I have been working with photos for the Arc of the Hill Country site, and many of them have lighting issues. Some of the issues just can't be fixed--like a large light overhead casting a terrible glare. The problem with glares is that they create an absence of color and texture, so there's not really anything underneath to work with. The other problem has been a red tint to the skin of many of the subjects. I finally found this workaround, using a hue/saturation adjustment layer:
First, copy the layer (ctrl J), then...
1. Open a hue/sat adjustment layer, and select "reds."
2. Take the left eyedropper and click over the deepest red that needs to be fixed.
3. Next, take the eyedropper on the right ( - ), and click the skin tone you'd like to match.
4. Move the hue slider all the way to the left. The image will turn into magenta/blue one. Don´t worry.
**Now, look at the gray area between the two rainbow bars. There are two tiny tics within this area. Grab the tic on the right and move it to the left until only the area you want to fix has that magenta/blue stuff going on. It's okay if areas beyond the subject are selected--you will be erasing those later.
5. Move the hue slider to the right, beyond the original position until you reach your desired skin tone.
6. Now, merge the adjustment layer with the layer below.
7. Use your eraser, set with a hardness of about 50%, and erase the areas that you didn't want changed--for instance, someone's red shirt, or shoes, etc. Sometimes there will be nothing to erase...
8. Finally, merge down one more time, and you're done!