Fix variant colors

[tool4ever]

Closes #11629

[Jetz72]

Hmmm. I think I wrote that that way to account for if a variant specified a mana cost with a different set of colors than the original card. By default color derives from mana cost, so if neither the original nor the variant specify a color indicator, it'd make sense for the variant's color to derive from its own cost.

I suppose we could make the variant's color derive from its cost only if it specifies an override for the original's cost, and otherwise inherit the original's color.

[tool4ever]

oh yea good point, I can try and tweak that later