>>112034
First load the image into a photo editing software, Photoshop is best but GIMP works too and it's free. Duplicate the layer.
The way I do it is then I select the subject. I used to manually use the lasso tool or pen tool, because I used GIMP (which is free), but now I have Photoshop and their "select subject" feature works pretty well. Then I adjust the selection to only be the skin, and I make a mask of the selection. If you can't get the selection right, you can still edit the mask later.
Then, I go to image>adjustments>channel mixer, and set the red channel to blue:100%, red 0%, and I set the blue channel to the opposite.
Then in the same adjustments menu I go to curves, and lower it so the blue is a bit darker, almost so it looks too dark. Then I go into shadows/highlights and make it brighter again. Then I go to hue/saturation and set hut to +4 to add some purplish highlights, and I play with the saturation till it looks natural (usually I lower it)
Then I just clean up the edges by fixing the mask and using the blur tool, and it's good to go. If you want to add swelling, the liquify tool is good for that.
For the most part, just experiment with the tools I mentioned and you should be able to make something decent
Feel free to ask any questions and I might post some pics with examples later