Proposal: revamp Idle doc 'Syntax Color' section

In https://bugs.python.org/issue25225
I propose to rename, demote, condense, and revamp the Syntax Colors 
section of the Idle doc.  The content change would be to drop the 
default color listing, which predates the Highlighting dialog that makes 
it obsolete, and instead better describe what text is being colored.

The last post has the proposed new text.  Any comments before I change 
idle.rst and apply?

-- 
Terry Jan Reedy