Attached is a patch to allow toggling of the ColorDelegator. It can be toggled using the existing, but undocumented, Control-/ binding. 

The patch modifies the "toggle_colorize_event" to fully remove coloring or fully recolorize the text rather than its existing behavior of disabling/enabling the coloring "thread." It also ensures that a ColorDelegator instance exists in every editor window instead of only those where ispythonsource returns True.

Toggling also works in the shell, but turning highlighting off fails if you start typing again. This is due to issue13495.

The crashing of IDLE described by Tal is likely due to pythonw.exe and is addressed in issue13582.