Use the Channel Mixer command to increase or decrease the red, blue, or green color channel by a percentage of itself and the other two channels. Use this command when you want to adjust color channels individually.
Important: To apply this command to a selection, the image must be a 16 million (24-bit) color image (otherwise the command is applied to the entire image). To increase the color depth of an image, see Increasing the Color Depth of an Image.
To use the Channel Mixer command
To limit the correction to a specific area, make a selection in the image. See Using the Selection Tools.
Do one of the following:
To modify the image pixels directly, choose Adjust > Color Balance > Channel Mixer.
To create an adjustment layer, choose Layers > New Adjustment Layer > Channel Mixer. For information on adjustment layers, see Using Adjustment Layers.
Do one of the following:
To maintain a color image, in the Output channel drop-down list, select a color channel to edit: Red, Green, or Blue.
To change the image to a monochrome (which looks like a greyscale but has a color depth of 16 million colors), mark the Monochrome check box. The Channel drop-down list displays Grey. When you adjust the color channels in the next step, you change the amount of each channel that is used to create the monochrome image.
In the Source channels group box, use the Red, Green, and Blue edit boxes or sliders to change the current percentage of that color in the channel you are editing. For example, if you are editing the Red channel and set the Red value to 50%, you reduce the amount of red in the image to 50% of its original amount.
To brighten the color channel, drag the Constant slider to the right. To darken the color channel, drag the slider to the left. The default of zero is the original setting.
Click OK.
Adjusting the Hue Saturation and Lightness in Unison
Changing the Color Balance of Shadows, Midtones, and Highlights
Changing the Overall Color Balance
Correcting Colors by Setting Black and White Points