Well, colors have their meanings.
Grey means neutrality, security, reliability, maturity, intelligence, modesty.
Blue (which is the only color you see in the previous screenshot) means trust, loyalty, wisdom, confidence, intelligence, faith, and truth.
That's why office applications will be in grey, with a touch of blue sometimes (but that seems to tone down).
Other colors you'll see almost never in business applications (red:danger/emotion, yellow:joy/creativity, green:health/fertility)
I guess with the recent problems of security SF had, they wanted to profile them more in that grey, secure, reliable, mature, neutral color.