Observe the faces in post #1305956. Ryuuichi is/was fond of giving character markings on their face: Keine has a full-blown third eye, Satori has hearts, Tojiko has lightning bolts around her eyes, etc.
And given how their eyeshadows stay on regardless of anything, those may be tattooed on, too. I've seen tattooed makeup, so I wouldn't be surprised.
If so, I for one am pleased with the development. They didn't really fit most of the characters, neither did the heavy make-up. Guaranteed, it looked good in choice few characters but not all of them. He has a personal enough style without putting them on everyone.