While I don't necessarily disagree with a mobile version, at least minimal coloring would be useful. The current version blatantly violates the principle of least astonishment, not to mention a very explicit declaration by @Jeff Atwood♦ that Meta <-> greyscale - I keep catching and working around the
UnexpectedSiteException ("Huh - greyscale? How did I get to Meta? Which site is this? Oh, it just looks like Meta, meh. Now, where was I again?").
Therefore, this new design keeps pushing me from using SO to thinking about SO; needless to say, this is rather disruptive, and I have noticed that I now avoid SO on mobile, as it's behaving very differently from the normal view.
I'd take a wild guess and say that I'm not entirely alone in this regard.
TL;DR: the current decision that "mobile shall only have greyscale" is a major UI blunder, pushing mobile users away from SO.
EDIT: My cries have been heard; rejoice, rejoice, color is back!