Red Atherytes.

[Jinrya-Geki]

What happened to Red Aetherytes idea from the concept art? I thought I remember they were supposed to be all red, but they're still blue.

[Enkidoh]

Red aetherytes were the old ones that were drained of aether by Atomos rememeber? All the old aetherytes were destroyed in the Calamity, although the one at Camp Revenant's Toll seemed to have exploded and is now a huge orange crystalline mass, which I think is based on that piece of art you're referring to.

In any event, the current aetherytes are brand new ones constructed after the Calamity, so that's why they're still blue, baring a return of Atomos to drain them again of course.