diff -r 4752fafb579d Lib/idlelib/ColorDelegator.py
--- a/Lib/idlelib/ColorDelegator.py	Wed Jul 11 19:21:31 2012 +0200
+++ b/Lib/idlelib/ColorDelegator.py	Thu Jul 12 13:47:43 2012 -0500
@@ -133,6 +133,10 @@
         if DEBUG:
             print("auto colorizing turned",\
                   self.allow_colorizing and "on" or "off")
+        if not self.allow_colorizing:
+            self.removecolors()
+        else:
+            self.notify_range('1.0', 'end')
         return "break"
 
     def recolorize(self):
diff -r 4752fafb579d Lib/idlelib/EditorWindow.py
--- a/Lib/idlelib/EditorWindow.py	Wed Jul 11 19:21:31 2012 +0200
+++ b/Lib/idlelib/EditorWindow.py	Thu Jul 12 13:47:43 2012 -0500
@@ -685,13 +685,13 @@
     def _addcolorizer(self):
         if self.color:
             return
-        if self.ispythonsource(self.io.filename):
-            self.color = self.ColorDelegator()
-        # can add more colorizers here...
-        if self.color:
-            self.per.removefilter(self.undo)
-            self.per.insertfilter(self.color)
-            self.per.insertfilter(self.undo)
+        self.color = self.ColorDelegator()
+        if not self.ispythonsource(self.io.filename):
+            self.color.allow_colorizing = False
+
+        self.per.removefilter(self.undo)
+        self.per.insertfilter(self.color)
+        self.per.insertfilter(self.undo)
 
     def _rmcolorizer(self):
         if not self.color:
diff -r 4752fafb579d Lib/idlelib/help.txt
--- a/Lib/idlelib/help.txt	Wed Jul 11 19:21:31 2012 +0200
+++ b/Lib/idlelib/help.txt	Thu Jul 12 13:47:43 2012 -0500
@@ -226,12 +226,14 @@
 	Return while cursor is on a previous command retrieves that command.
 	Expand word is also useful to reduce typing.
 
-    Syntax colors:
+    Syntax Highlighting:
 
-	The coloring is applied in a background "thread", so you may
+	The highlighting is applied in a background "thread", so you may
 	occasionally see uncolorized text.  To change the color
 	scheme, use the Configure IDLE / Highlighting dialog.
 
+	Use Control-/ to toggle syntax highlighting.
+
     Python default syntax colors:
 
 	Keywords	orange