(1) their favorite colorway in the sale:
At first it was easy: Liquid. But then I saw Elite Nacre and couldn't resist, even though I have nothing that will pair with it.
(2) what non-keyboard-related thing it best matches, in their opinion:
As for Liquid, a lot of things I own have the black/blue/white theme going on (desktop wallpapers, mobile wallpapers, themed software, etc.).
<3