Boros... Control? Without doing the smashy and the swingy and the legions of soldiers ready to become cannon fodder? Why, sirs, madams, and gender neutral honorifics, step this way.
EMN standard has a crazy amount of board control in white. Stasis Snare, Isolation Zone, and Quarantine Field from BFZ/OGW, and Silkwrap from DTK. Spot Removal for days. So why not build a creatureless deck that gets you stupid value from Sigil of the Empty Throne and Starfield of Nyx?
"But Ross!" I hear you cry. "Why are you running it with red? Why not blue?". The answer, as to a lot of important questions, is pretty simple.
Blue's non-aura enchantments are, by way of comparison, poor.
Sure, Blue gets you Lunar Force - which in a starfield deck, is a powerhouse, and is part of why the provisional sideboard runs 4 Port Town. Otherwise? Your options are a little underwhelming. Sphinx's Tutelage is decent (and makes the sideboard) but otherwise, they don't cut the mustard; or alt least, not in the field wide sense. Auras? blue has decent ones, but I digress.
Red on the other hand, gets you some really interesting little combinations. Molten Vortex lets you start pitching land if you need a little something to get over the line, while Blood Mist is just a solid card once Starfield of Nyx is online.
But Red's MVP in the deck is Flameshadow Conjuring. it doubles down on rempval for a turn; it gets you a bigger Vessel of Ephemera which can get spirits from; it can nab you another Sigil of the Empty Throne for a turn, which, if you have enough mana to throw down a cheap enchantment: Quarantine Field where X = 0, for instance, then you're nabbing 2 4/4 fliers
All in all, it's an interesting deck, and well worth giving a go