Wait, FFII HAS Holy o_O
And I've always thought that Flare, as Black Magic, should be the opposite of Holy, as White Magic... and above them, Meteor, as Black Magic, should be the opposite of Ultima, as White Magic.
And FFVIII's and FFX's Ultima have strange colors. But they are so strange, that each people says a different color. xD
And I agree and disagree about Doomsday/Ultima. It'd make more sense if Kuja busted you with Doomsday, since it's such a "apocalyptic" magic. But Ultima is special. And besides, if Vivi could use Ultima, Flare would be obsolete. Since by the Disc 4, Vivi should have Half MP... plus, Ozma would be IMPOSSIBLE to the Lv1 Ozma Challenge if she used Ultima (remember, Doomsday would be Kuja-only). She could kill you by Ultima-Curse, Curse-Ultima, and the default Meteor-Curse; and Doomsday is a breather in this battle, if you absorb Shadow/do the Friendly Monster quest/both.