Many applications (e.g. Xcode, Pixelmator) can launch OS X's standard color picker tool window (seen below) and others (e.g. the font picker). These tool windows look almost like regular windows, but they have a shorter title bar and the three gumpdrop buttons at left are slightly smaller too.
What I'd like to know is: How can I close such a tool window, using only the keyboard?
I've tried Cmd+W but it doesn't work for this kind of window. Rather, Cmd+W seems to cause the parent window to want to close instead. What am I missing?