Black works always. Why not black?
I can't understand beige choice. It's too close skin color of some Inquisitors which might make them seem naked. Also it don't look that good, the color is wrong and whole thing looks like pajamas with same coloring on top to bottom.
I've thought about that and came up with a crackpot theory (that just might be true!): in black, the outfit might look like a Mao suit. Well, a Mao suit with Ugg boots, I grant you, but in most story-forwarding views we can't see the boots. Maybe a Mao-suited inquisitor produced too much cultural dissonance?
I did notice that in beige I blend into my walls and parapets outside really well. That could come in handy...