Okay, so I'm not having any problems with followers in their AI or other functions except for their skin tone appearance in the game.

The head color and body color are not mismatched, they are just both stuck on the default color for the respective races. I have changed them and saved them in the Creation Kit, and the view window of the characters reflects the colors I want, which are not custom colors.

Example: I have an Argonian follower that I want to have the red preset skin color for his body and head. I've changed his skin tone to this color in the Creation Kit and saved, but when I load up my Skyrim file, he appears the default green skin tone color.

I've already done the CTRL + F4 part to export his facial markings, and the warpaint on his face is showing up correctly in-game.

I'm very new to modding with the Creation Kit (and modding in general), so if anyone is able to help me, I really appreciate it.

Do you have texture replacers installed? You need to do facegen exporting with the vanilla textures only.

Yes. I have recently tried saving it with and without the body texture replacer, but it still shows up with the default color on my Argonian character.