I don't want to raise this as a confirmed bug as yet, as I'm not sure if it's just me. Was going to start a new vampire play through, and I know some of the vampire mods on PS4 have gray face issues, so I loaded only the USSEP and the ones I wanted to test, Serana's Eye Options, No Fur / Skin Changes for Beast races, and No Wrinkled Vampires, and ran a new game.
I went straight to the closest known vampire, the female NPC at Half Moon Mill (Hert). Sure enough, she had the grey / purple pixellated face. I disabled all the vampire related mods leaving only USSEP active, and the face bug remained. Disabled USSEP and the face reverted to normal. Re-enabled both vampire mods without USSEP and the face bug did not return.
I can't determine as yet whether this affects all vampires, but it does seem that the USSEP is the cause. Has anyone else had this occur on PS4, or is there anything in the changelog that would suggest a PS4 incompatibility due to the lack of external assets and scripts?