The rc.15 build has the file bowser with new source list style. The color of a selected item in the file browser can be quite difficult to see sometimes (depending on what’s behind the window). I’ve included three screen shots, from TextMate, Xcode and Finder. The location of the selection was the same for all application (the same thing behind the window). What’s behind the window is my desktop with a blue color. In the TextMate screen shot it’s the “package.d” file that is selected.

This is on macOS 10.13.