I'm not really up to date on MtG lore, as I stopped playing during 4th Edition. But this: "[Usagi]'s not Colorless, she's every color." That part is obvious from the original anime. All of the senshi have a color, but Usagi's final form is pure white. It's the composition of all of the colors, and the expression of all of the wishes of her allies/court. She was even supposed to be a white-haired bunny until editors made Takeuchi-sensei change it.
Usagi isn't white in the sense of MtG; that would be more of a yellow. But I would say that the mapping is pretty good from sailor magic to MtG magic: Minako is white, Rei is red, Ami is blue, Minako is green, and Mamoru is black. Only the last one is a bit of a stretch, and that's because MtG black has a more eeeevil tone to it. At least it did when I still played. But these are all based on universal symbolism anyway, e.g. 火星 is the fire star is the red planet is Mars is destructive is passionate.
Usagi isn't white in the sense of MtG; that would be more of a yellow. But I would say that the mapping is pretty good from sailor magic to MtG magic: Minako is white, Rei is red, Ami is blue, Minako is green, and Mamoru is black. Only the last one is a bit of a stretch, and that's because MtG black has a more eeeevil tone to it. At least it did when I still played. But these are all based on universal symbolism anyway, e.g. 火星 is the fire star is the red planet is Mars is destructive is passionate.
"Kitto daijoubu da yo." - Sakura Kinomoto