It's black and green just like Winding Constrictor because its mana cost has B and G in it
Blue Mana Ramp for Instants and Sorceries (Curious Homunculus, Karfell Harbinger, Unblinking Observer, Volshe Tideturner) Given how intertwined blues color identity is with instants and sorceries, Im really glad to see Wizards of the Coast dipping their toes into conditional mana dorks that can only use their mana for these types of spells
Without these the Onion Knight is pretty much a Joke Character
To double Tifa Lockhart's power, it gets +X/+0, where X is Tifa Lockhart's power when the landfall ability resolves
When that spell or ability resolves, Dovin's Veto won't be countered, but any additional effects of the countering spell or ability will still happen
You would use your hand quickly to get your opponent on the ropes, then hammer them with the Scroll now that your mana wasn't busy