This seems very blue, in both name and ability.

I know, but Kosmen is the head of the white-aligned faction, which wants to unify the world into a single mind. Flavorfully, that's white, and the abilities make sense for the flavor. It's a shame that Memnarch is blue.

Well, it's not just Memnarch. Blue is the colour that most cares about artifacts, and blue is overwhelmingly the colour that steals control the most. (With black in second, assuming we're ignoring red's temporary stealing. This seems to be evoking Preacher, which is really quite old, and Evangelize, its Time Spiral throwback.)

The flavour of hive minds sounds blue or green. I guess it's got things in common with Selesnya. But this card still looks like Master of Etherium crossed with Beguiler of Wills.

You can't break the pie for flavor. This is blue.

Unifying everyone as a white leader - that's fine.

And it's mythic... But yeah; mechanically - it pumps from artifacts, and steals artifacts.

That makes it red, right? (Hellkite Igniter, Aladdin)

It's certainly not white, though. Colourless potentially.

I'd argue that P/T equal to number of artifacts, while often blue or colorless, can apply to white here, since this set has creatures=artifacts. This is a type-shifted Geist-Honored Monk that makes sense in set. The Steal Artifact is too blue, however.

Yeah, I can see white getting the Master of Etherium ability in an artifact set.