It's interesting that Microsoft chose to adopt monochrome icons after Mac OS X / iTunes adopted monochrome icons. I'd be curious if Apple's design was a major influence on Microsoft's designers, or if the idea for monochrome icons came primarily from independent research/user testing.
This looks more like an extension of the UI style they started adopting with the Expression tools back in 2008, which itself was more directly influenced by Adobe tools like Photoshop Elements and Lightroom than iTunes or Mac OS.
If you really want to tie Apple into it, then the anchor would be Aperture (which obviously influenced Adobe), not really iTunes or recent releases of Mac OS.
FWIW, I first noticed the "use monochrome icons to reduce distraction" approach in Windows 7, when it was applied to the default system tray icons. I think that predates the Apple trend (but I don't follow Apple closely enough to know).
I suspect these kinds of things tend to just be general "design" trends though - I bet the people designing these interfaces probably talk to each other, subscribe to the same magazines, read the same articles, follow the same non-software industrial designers and artists etc.
