Transform Ordinary Skin into Red

Step 1. For this tutorial I'll use photo of woman eye.

Step 2. Copy "background" layer using Ctrl + J on keyboard. Name new layer "normal_eye".

Step 3. Go to Create new adjustment layer and create Channel mixer and press OK. Go again on Create adjustment layer and click Hue/Saturation and click OK. Now, we have to make these two layers to be clipping mask of "eye" layer. Click on Channel mixer and then go to Layer - Create Clipping Mask. Repeat this with Hue/Saturation layer.

Step 4. Now we have to work on Channel mixer and Hue/Saturation. But first we have to mask eye on the photo. Click on Channel mixer mask (be sure that it is filled with white), pick brush, select black color and paint over eye (or you can use Quick mask mode if you find this approach easier).

When you are done with mask press Alt key and drag mask to the Hue/Saturation mask above it. Release it and you'll be asked if you want to copy it over existing mask. Click Yes.

This is how it looks

Now for the Channel mixer set these values

Red

Green

and blue

and for Hue/Saturation these

Red

and master

Step 5. Now merge all visible layers into one by pressing Ctrl + Alt + Shift + E. Name this new layer "red skin".

Step 6. Click Create new adjustment layer, select solid color and use this value #13bebe for color. Press OK. Now we have to select everything on the photo except the eye. So mask the eye and invert selection using Select - Inverse. Fill selection with black. I've got it looking like this

Step 7. Set Blending mode of layer to be Color and opacity to 45% and we are finished

See you!