The curves adjustment dialog allows you to apply up to six nodes to experiment with color values. Using the white, gray and black set point droppers gives immediate color correction to digital images.

Once your photo has been corrected for brightness and contrast, you may want to take a look at what color correction can do. You can either use the Color Balance sliders, which allow you to adjust colors between the complementary values of Cyan/Red, Magenta/Green, and Yellow/Blue. Or you can try the Curves adjustment, pictured above. Since this method can result in rather bizarre color shadings, be careful of how you use it!
Once Curves are mastered, however, you can apply fine control to your color balance.

To the left is a picture taken in a school hallway. It looks as if there is a yellow wash over the entire picture.

After applying Curves white and black set point droppers for color correction, the picture to the right shows blue blues and white whites. The background wall still appears yellow.