How: Customize look of Safari's Location bar and other Toolbar buttons?

[Jess13]

I like how Quick Look and Safari inactive have subtly outlined Location bar and Toolbar buttons, I would like to have similar outlines for Safari active. I looked in Safari's resources but couldn't find the image files to replace. Is this possible, in Safari or system-wide? If yes, please tell me how. Thank You.

 

[redheeler]

Wait for OS X 10.11. Active window toolbar buttons there have an outline.

 

[Jess13]

Wait for OS X 10.11. Active window toolbar buttons there have an outline.

View attachment 566466

Sweet.