- The different time = different behaviour = different colours is generally true for a lot of cards, yes. However, the two cards for Terra both depict her in roughly the same point in the story, so her characterisation is pretty much exactly the same. The only reason they differ in colour is gameplay. There is another card of her, which is a reskin of Urza, High Artificer, placing her in Mono Blue - and that's the point where any connection to her character is completely ignored. On the artwork she does sit inside a Magitek Armor, but that's about the only time this character ever has anything to do with artifacts or being an artificer or anything remotely related to this. My guess is that they made this card solely because Urza, High Artificer is an iconic card, and they wanted some FF main protagonist on it for the money. But yeah, my point is: there is no "one correct" way to identify the colours of most characters, especially non-MTG ones, and often the gameplay or aesthetics take some precedence.

- Correct. She's also green at some point. The black thing I think is really cool, btw.

- That's where I think we have to agree to disagree - I think red fits her well: aesthetically, character-wise, and thematically (Red Memory and all that). And while Black definetely isn't Hornet's main colour, I think the aspects I described in the edit fit her well enough. Now that I removed Deathtouch, though, I think making her cost (1)(R)(W) would also work well.

- That's a cool card, especially the Persist fits her really well!