Why is every popular website removing colors?

I didn't know where to ask, so I'm trying here.

I don't know if you guys have noticed, but youtube (logo, like/dislike etc.), facebook (like & comment icon), g+ (same) etc. have removed all colors, applying only gray scales. IMO it is really bad, makes it more difficult to notice if that button is pressed or not.

Second, on mobiles, popular apps including facebook, gmail etc. have started to include an in-app mini-browser.

1. Why in the world would they remove colors where it counts?

2. Why do they always copy each-other exactly and immediately?