bpo-33656: Mention color in idlelib/NEWS.txt entry. (#7646)

Lib/idlelib/NEWS.txt

@@ -6,10 +6,11 @@ Released on 2018-06-18?
 bpo-33656: On Windows, add API call saying that tk scales for DPI.
 On Windows 8.1+ or 10, with DPI compatibility properties of the Python
 binary unchanged, and a monitor resolution greater than 96 DPI, this
-should make text and lines sharper.  It should otherwise have no
-effect.  If perchance it make text worse on your monitor, you can
-disable the ctypes.OleDLL call near the top of pyshell.py and report
-the problem on python-list or idle-dev@python.org.
+should make text and lines sharper and some colors brighter.
+On other systems, it should have no effect.  If you have a custom theme,
+you may want to adjust a color or two.  If perchance it make text worse
+on your monitor, you can disable the ctypes.OleDLL call near the top of
+pyshell.py and report the problem on python-list or idle-dev@python.org.
 
 bpo-33768: Clicking on a context line moves that line to the top
 of the editor window.