I'm fairly sure this is a reference to the pokemon Ho-oh, but I'd like to see if someone agrees with me before tagging it as such.

I think it is too, the title has "Toraumahouou" トラウマホウオウ

phoenix are actually colored in more colors than just red and orange. Since Mokou's spells are inspired by the phoenix, it makes sense artists will use the real color scheme

ah.