re Tk System colours

In sorting out some colour issues for an application I found what I take
to be standard settings such as:
1.	SystmeButtonFace
2.	SystemDisabledText
3.	SystemWindow
4.	SystemWindowText
 
I could not see any reference to these in Mastering Perl/Tk and my web
search did not reveal anything very useful.
 
Therefore I wondered if anyone:
1.       knew of a complete list;
2.       could explain how to get the RBG (or something equivalent)
value for each of them.
 
Best regards
 
Henry Merryweather