really really quick way to do zombie with great results and go from the original photo to the zombie hope you enjoy

Step 1: Starting Phase

step one: find ur scene and model :)

step2: now open the picture(s) up on pixlr

Step 2: The Middle

step 3: go to layer (which is next to image on the menu bar) then while having the background layer selected duplicate the layer.

step 4: go to the copied layer and make a mask around the subject using the lasso tool.

step 5:then with the copied still selected go to the adjustment menu and click hue and saturation move the first slider only mine was at 103 for that greenish tone play around with it to achieve your desired color.

Step 3: The Ending/optional

optional
step6: on the original use the adjustment old photo from the adjustment menu to give it a better of more delirious unearthly feel sometimes seen in zombie movies

step7: create or find some fake blood assets and add them it is easy if done on a transparent background like using Photoshop and its brushes make sure that it is a .png file and if you do the blood remember to put it on its on layer and repeat step 6

ill attach the file i used for blood so that those who cant make or find blood can have it and yes it is allow transperant when u download atleast i think so enjoy and have fun :3 happy halloween