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You can use a Hue/Saturation adjustment layer to change individual colors in a photograph.
Making a change to a single color only changes that color.
The complementary color is not changed.
In contrast, if you use a Levels adjustment layer to change a single color, the complimentary color is also changed.
That's often a disadvantage.
So, you may want to use a Hue/Saturation adjustment layer.
Here's the Hue/Saturation window.
Be sure to check off as you go along.
1) Create a Hue/Saturation adjustment layer.
The Hue/Saturation window (above) will open.
Make the adjustments described below.
Click OK (Pre-8.0 only).
2) Select a color in the box that has Master inside the box.
Use the Saturation slider to change the color.
To learn how to determine which color to change, go to Measure Color.