Provide sample window for Appearance pref

[BeOSR]

Appearance pref could do with a sample window that would highlight and show changes. While several entries of the colors list are obvious, like Window Tab or Tooltip Text, others are quite unclear, like Shine, Navigation Base,... An sample window showing *all* possible parts, highlighting the selected one and updating changes immediately would be very helpful.

[jscipione]

Assigning this to myself as I am taking a look at the Appearance prefs right now