Tsukuyomi literally translates to moon reader in English. This is possibly personified in the blue Ash as it appears to have a more calm, nightly presence. Given that Ash is basically the ideal ninja I also made a connection with the Naruto series in that Tsukuyomi is a move used by one of the cahracters, Itachi. The move is an illusion move that is shown in the colors of black, red and white but mostly black and red. Itachi himself is also cloaked in black and red. This same color scheme is in the other skin. That skin also has a more Arkham Knight kinda feel as the helmet bears resemblance to Batman's bat themes. Batman also being a stealth, ninja-like charcter parallels Ash's prowess in the ninja arts. These were long streches so I kept researching. To connect both to the same thing, I came across a story shared by various cultures of a rabbit that lived in the moon. The story goes that a handful of animals were to give charity on a full moon. The others cheated or made good their promise but the rabbit who could only gather grass instead offered itself and jumped into the fire to cook. The poor man they had helped turned out to be a deity and because the rabbit's sacrifice the rabbit was forever imprinted on the moon. Looking at the red skin the helmet could be showing rabbit ears. Its red due to the rabbit jumping into the fires. The blue one however is the aftermath. Its presence is now bound to the moon giving it a much rounder texture than the sharpness of the red skin. My best guess is the theory of the skins being based off the rabbit as it combines colors, texture, and overall presence into one.