Color replacement using the HUE blending mode

For this tutorial we’ll be using the HUE color mode to replace an image’s color without affecting the underlying contrast or luminosity.
1. Create a selection that represents the area you want to adjust. Depending on the image this can be either a straight forward selection using the quick selection tool, magic wand or path tool OR it can be a little more involved that will require editing in the QUICK MASK. Either way we set up, we’ll ensure we provide flexibility into our editing workflow so that we can dynamically adjust the selection later on if we need to. (For the dragon image I used a IMAGE > calculations to create a new channel from the Blue and Green Channels using ADD as the blending mode with an offset of 100 and a scale of 2, then made the new channel high contrast using levels and then finally manually deleting extraneous details. This process yielded a selection that included all of the bright green plus some reflections of the color throughout the image.)

the modified alpha channel to be used as a selection

2. Save the selection. SELECT menu > SAVE SELECTION. Name it if you want or use the default ALPHA 1. If you used calculations to make the Alpha channel you will not need to do this step as calculations made a new channel for you.

3. Load the selection. SELECT menu > LOAD SELECTION > choose your selection.

4. Make a new SOLID FILL ADJUSTMENT LAYER and select an appropriate color (this can be changed anytime)

5. Change the LAYER MODE to HUE. This will retain the color from the adjustment layer and the contrast from the original image. Change the color of the Adjustment Layer by double clicking the Color Fill thumbnail.

6. If you need to edit the selection, click on the Color Fill Layer Mask thumbnail to activate the mask as an alpha channel. Go to the CHANNELS panel, make the alpha channel visible (Color Fill 1 Mask) by clicking on the eyeball icon. You can now use any of the editing tools to modify the mask used for the color adjustment.