Admittedly I don't pay that much attention to the competitive scene, but it seems that barring something like Jeskai Ascendancy competitive red decks are always Mono-Red? Like, I get why that is, the red strategy tends to really hurt for the potential loss in speed that comes from diluting the mana base, but (assuming I'm right at all) how might they develop Red to play better in multicolor decks?
The thing is, Red is the finisher. It's typically the color with the best early game and the one that has the easiest time getting in the last few points of damage when the board stabilizes. For the late game, Red gets Elkin Bottle effects, like Outpost Siege, but you'd rather get straight card draw from another color in most decks.
On a color-by-color basis:
Red and White will always be aggressive. They're both weenie colors, traditionally and neither gets much card advantage which hurts their long game.
Red and Blue can work as either control or tempo since red gets decent removal and blue gets lots of control cards. The real issue is, Blue/Black will typically be better because black gets better removal than red and better card advantage (even though blue supplies that itself).
Red and Black are both great at creature removal, but not so great at dealing with non-creature permanents. They tend to be aggressive, since you want to capitalize on your opponent's field being clear, but I don't think they have to be. For a more controlling deck, they'd need to push black discard more than they're comfortable with, I think.
Red and Green can play both aggressive and midrange pretty well, but since green's card advantage is tied to creatures, they don't work as well for control. In order for them to play control well, I think we'd have to see more, competitive, green hexproof creatures, and I don't think most people are especially interested in that.
The best ways to get decks other than mono-red decks to play red are: multi-color cards with red in the cost and non-burn, non-removal red spells that compliment what other colors want to do. Some good examples in standard:
- Circle of Flame (sideboard card, but it encourages a more defensive play style)
- Anger of the Gods (decent sweeper that punishes aggro strategies)
- Crater Elemental (great blocker that favors a more midrange strategy)
- Kurkesh, Onnake Ancient (encourages a more combo-based deck rather than an aggressive deck)
The thing is, these types of cards are rarely pushed and generally require a lot more support than a typical red build.
