I thought i would share a technique that i learned on how to fix the white balance in photos using photoshop. I use it every time i edit it's the first thing i do even if the color looks okay anyways.
Hope it's helpful for others like it has been for me . I've also will be adding this my tutorial/action blog so it can be found there.
1. Add a new layer either by click on the new layer icon in the layers window or by click on layer - new - layer
2. Fill the new layer with 50% gray. To do this click on edit - fill - 50% gray
3. Change the fill layer to difference mode under the layers window
4. Add an a threshold layer eiether by click on the adjustment layer icon in the layers window or by click on layer - new adjustments layer - threshold
5. Next, in the threshold adjustments window move the adjustment slider clear to the left so that the adjust level is set to 1.
6. Next, Double click in the threshold layer. Move the slider all the way to the left and the image becomes white. Slowly move it back to the right and you will see some black areas reappearing on the image, those are the gray areas in the image. Click Ok.
7. Next, click on the color sample tool and then zoom in on the black area that you want to sample and click on that area. I tend to keep the sample size at point sample but some suggest using 3x3. I find better results with the other size.
8. Next, after you have your sample selected delete both the threshold & fill layer and then zoom in on the sample point.
9. Next, create a curves adjustment layer. In the curves Dialog Box take the gray eyedropper and click on the sample point that you just created.
You should now see a big difference in the white balance of your photo.
Here is a before and after to show you how it can improve your photo.