Firstly, there is no easy and simple way to achieve a natural looking tan in Photoshop.

The method below is one that I have used previously, but it does require a lot of patience to build up the skill levels to be able to see and judge what is a natural looking Tan and what isn’t, and saying that, it still does not work for every kind of image.

The idea is to introduce the Tan in separately for the Shadows and Highlights. Otherwise, it can make the Shadows even darker and a bit “Dirty”.

Once the Tan has been applied evenly, then you need to selectively color grade the image.

There are 3 steps to the process

Step One – Highlights

1. Create a solid fill adjustment layer – choose a natural looking orange of your choice (remember it can be fine-tuned later)
2. Change the blending mode to Color Burn
3. Next, click on “fx” to work on your Layer Style
4. Ensure Color Burn is selected in Blend Mode
5. At the bottom of the panel, ensure “Gray” is selected next to Blend If.
6. Now, holding down the alt key, slide the right side of the Left pointer of the underlying layer from Left to Right
7. This will now split the pointer and remove the blending effect from the Shadows and only effect the Highlights
8. Now Click back on the Solid color and adjust the color to fine tune. (This requires patience to build the skill levels)

Step Two – Shadows

1. Create a solid fill adjustment layer – choose a natural looking orange of your choice (remember it can be fine-tuned later)
2. Change the Blending Mode to Multiply
3. Click on “fx” to work on your Layer Style
4. Ensure Multiply is selected in Blend Mode
5. At the bottom of the panel, ensure “Gray” is selected next to Blend If.
6. Now, holding down the alt key, slide the left side of the right pointer of the underlying layer from Right to the Left
7. This will now split the pointer and remove the blending effect from the Highlights and only effect the shadows
8. At this stage, you may also want to slide the second underlying Layer from Right to Left to fine tune
9. Now Click back on the Solid color and adjust the color to match to fine tune

Step Three – Color Correction

Here you have to remember the Rule about Opposite colors

1. Cyan is the opposite of Red
2. Magenta is the Opposite of Green
3. Yellow is the opposite of Blue

Once again, you will need to build your skill levels.

1. From the Adjustment Layers – Choose, Selective Colors
2. Starting with Red, work on the Cyan, Magenta and Yellow
3. Move the sliders until you have reached your desired color effect

Remember, you can always go back to each Solid Color Layer and adjust the Hues as you wish. Same applies to the Selective Color adjustments.

Once you have achieved what you feel is the best you can do for now, Save it as an Action for future.

Hope this Helps