What are the names for Magic's different deck colour splashes?
I'd say the realistic answer to the question is &quot;those terms are not commonly used&quot;. Looking back through some recent tournament decks on the official Wizards site:

Simon Görtzen's Boros-splash-blue-splash-black deck at the October 2020 League Weekend is simply described as &quot;Four-color Cycling&quot;
All the Temur-splash-white decks in the Top 8 at the October 2020 Season Grand Finals are described as &quot;Omnath Adventures&quot; after their namesake card, Omnath, Locus of Creation.
The Temur-splash-white decks in the Top 8 at the July 2020 Players Tour Finals are described as &quot;Four-color Reclamation&quot;.