The lights are actually braille, dots resembling letters from the alphabet for communication for people who are blind or have low vision. But in this case the braille on the Regi's heads don't resemble any letter nor word. Although I believe this is supposed to be a Shem, something used for the creation of Golems, which is what the Regi trio is based on; golems. In Jewish folklore a Shem has to be written on paper and put in the mouth or the forehead - in this case the forehead of the Golem to create one. The Regi trio might get this as an inspiration for the braille on their heads. But then forming it a bit in their own way, like the Shem not being on paper and it being braille instead of written.
TL;DR:
The lights are braille that don't mean anything, but can be speculated to be Shem, something used in the creation of Golems.
That's all,
SeeYaLater!
