Background:

Caliente's Beautiful Bodies Enhancer,  or CBBE as we know it, has an feature in which (quote from CBBE page, Q4):

... FO4 CBBE's UV map is almost exactly the same as Skyrim's, making it easier for modders to convert body textures over or make new ones, and filling up the wasted space. But as a result, the part of the UV map used for the head is taken up by our leg texture.

In simplest terms this seems to mean that all and every single one of CBBE female skin textures (in Fallout 4) are missing rear head parts. And if left to default, rear head texture for females will be loaded from back of the right knee of the female body texture (this problem does not exist on males). This feature was fixed with CBBE.esp plugin:

The plugin corrects this by pointing the head rear to a duplicated, vanilla body texture (femalebhed.dds). The plugin is optional if you
have hair covering your head rear or can ignore the issue.

Unfortunately, CBBE.esp plugin does not fix this problem when using CBBE version of Ghouls Revamped. Almost all female ghouls with CBBE version of Ghouls Revamped will have some kind of rear head discoloration or texture miss-match.

There are other fixes that does same thing, but they did not work for my load order. And that is why I made this mod.

• Caliente's Beautiful Bodies Enhancer.
• Ghouls Revamped and CBBE version of it.
• Archive2.exe from Creation Kit Version 1.10.162.0 or later.
• From this mods Files section download main file Female Ghoul Head Rear Fix for CBBE version of Ghouls Revamped.7z
  

• Extract Female Ghoul Head Rear Fix for CBBE version of Ghouls Revamped.7z into a temporary folder. For example C:\temp\Ghouls_Revamped_Head_Fix.
  

• Since you are using CBBE version of Ghouls Revamped, you already have downloaded main file of that mod (it is a requirement). Main file of Ghouls Revamped contains archive named Ghouls Revamped - Textures.BA2. Use Archive2.exe from Creation Kit to extract all files from Ghouls Revamped - Textures.BA2 into a temporary folder. For example C:\temp\Ghouls_Revamped.
  

• From the folder where you extracted Ghouls Revamped - Textures.BA2, for example C:\temp\Ghouls_Revamped, copy following three files from subfolder \textures\actors\character\GhoulFemale
  

ghoulfemalebody_d.dds
ghoulfemalebody_n.dds
ghoulfemalebody_s.dds

• Into the temporary folder where you extracted this mods main file. For example C:\temp\Ghouls_Revamped_Head_Fix subfolder Textures\actors\Character\GhoulFemale_Rearhead_Fix
  NOTE: Without these three files this mod does not work at all.
• Use your favourite archiver (7-zip?) to zip contents of C:\temp\Ghouls_Revamped_Head_Fix
• Install zip file you created in previous step with your favourite mod manager.
• In your favourite mod manager, place plugin CBBE and Ghouls Revamped rear head fix.esp somewhere very low in your load order.
  

Done!

Technical details:

Plugin was made trough trial and error, but I think I managed to separate ghoul females and human females head parts from FemaleHeadHumanRearTEMP. Of course human females still uses FemaleHeadHumanRearTEMP, but ghoul females uses completely new record.

Compability:

I am pretty sure that this mod is not compatible with anything else except vanilla masters. So, to make this work with your load order, you may need to do some kind of editing in FO4Edit. For example, if you are using HiPoly Faces REDUX or M8r98a4f2's Complex Item Sorter you definitely need to do something. Either load order juggling or editing in FO4Edit.

Support:

Since I do not have almost none knowledge of how this actually works, I cannot give much of support to it. Also, please be aware that this mod could actually break something, but I have no idea what that could be. I will leave posts section open so anyone who has more knowledge about these kind of things could offer us peasants some guidance and correct our wrongful ways.