I am using tkinter and the PIL to make a basic photo viewer (mostly for learning purposes). I have the bg color of all of my widgets set to the default which is "systemfacebutton", whatever that means.
I am using the PIL.Image module to view and rotate my images. When an image is rotated you have to choose a fillcolor for the area behind the image. I want this fill color to be the same as the default system color but I have no idea how to get a the rgb value or a supported color name for this. It has to be calculated by python at run time so that it is consistent on anyone's OS.
Does anyone know how I can do this?
You can use w.winfo_rgb("systembuttonface") to turn any color name to a tuple of R, G, B.  (w is any Tkinter widget, the root window perhaps.  Note that you had the color name scrambled.)  The values returned are 16-bit for some unknown reason, you'll likely need to shift them right by 8 bits to get the 0-255 values commonly used for specifying colors.
Determining "SystemFaceButton" RBG Value At RunTime