Is a 6/6 Flying creature that deals colourless damage Mythic enough?

I was originally going to also give it : ~ gets +1/+0 Until end of turn. But, as is, anything with Prot Black and/or Prot Red is still going to fry in its colourless fires (Except for that pesky Baneslayer Angel due to the Protection from Dragons but hey, every card has to have some weakness).

Hmm. At the moment it looks more rare than mythic. Also, the ability doesn't technically work as phrased at the moment. You want either "~ is colourless" (at which point it'd want a colourless frame rather than the gold one, which is a change you might want to avoid), or "~ deals damage as if it were colourless". And I'm not sure that latter wording even works properly regarding Circle of Protection: Red.

Have gone with "Damage dealt by Ghostflame Dragon is considered to be from a colourless source." for now I was trying for just the damage to be colourless (partly to avoid Cops and Prot Black/Red) I think this wording may work ???

I was also considering giving it Ghostfire as an activated ability to really hity Mythic levels.

Yeah... Sadly that wording won't dodge Circle of Protection: Red either. It's because the CoPs have abilities you can activate a long time before the creature deals damage. When the CoP's ability resolves, you choose something that is (at that moment) red. The next time that thing deals damage that turn, the CoP ability prevents it - even if it's no longer red. And of course CoPs don't target. So to dodge CoPs, you either need the creature to be genuinely colourless all the time, or a very weird ability like "~ can't be chosen as a source of damage by spells or abilities".

You could just give up on dodging CoPs; the current wording does work to dodge protection - at least, if the protected creature blocks this one. Obviously this won't be able to block a Prot Red creature unless this is genuinely colourless as well.

­Ghostfire as an activated ability is a nice idea. I'm not sure how that would have to be phrased to even get around protection, though. Something like ": Choose target creature or player as though ~ were colourless. ~ deals 3 damage to that creature or player."

I'm happy to not dodge CoPs as they aren't seen very often, and I'm fine with this not being able to block Prot Red/Black/Etc creatures - you'll mostly be attacking with it anyway. I'm going to add the Ghostfire ability to it as well (That way if it can't attack for any reason it still has a use).

So he can only affect a Prot Red and/or Black creature by blocking it right? cause it's only the damage that's colourless not the dragon himself so he can't target them in the first place (correct?)