Color Correction Basics
Photoshop CS3 Tutorial
How to Color Correct an Image in Photoshop
Generally, if one part of an image has a color cast, the remainder suffers from the same color shift. A color shift can occur in one or two of six directions.
The six color directions are Red, Green, Blue, Cyan, Magenta or Yellow. The trick is to determine the direction (or directions) and adjust accordingly.
Open an image in Photoshop (File > Open...) that has an obvious color shift.
Select the Eyedropper tool with the Info palette open (Window > Info).
Take several samples in the image that should be white, black or shades of gray. Watch the values in the Info palette. The shades of gray should have equal red, green and blue values.
An image that has decreased blue values is heavy in the yellows. Blue and yellow are across the color wheel in Photoshop. Along the same logic, green and magenta are opposites as well as red and cyan.
To add more green to a magenta image, add a Color Balance adjustment layer by clicking the Adjustment Layer icon and selecting Color Balance.
With Midtones selected move the center slider towards Green. Repeat the process for the Shadow and Highlights options if necessary.
PSD Color Wheel
For more information on Computer Color Wheel opposites, see topic PSD Color Wheel.