diff --git a/Lib/idlelib/config-highlight.def b/Lib/idlelib/config-highlight.def
index 7d20f78..4146e28 100644
--- a/Lib/idlelib/config-highlight.def
+++ b/Lib/idlelib/config-highlight.def
@@ -62,3 +62,32 @@
 stderr-background= #ffffff
 console-foreground= #770000
 console-background= #ffffff
+
+[IDLE Dark]
+comment-foreground = #dd0000
+console-foreground = #ff4d4d
+error-foreground = #FFFFFF
+hilite-background = #7e7e7e
+string-foreground = #02ff02
+stderr-background = #002240
+stderr-foreground = #ffb3b3
+console-background = #002240
+hit-background = #fbfbfb
+string-background = #002240
+normal-background = #002240
+hilite-foreground = #FFFFFF
+keyword-foreground = #ff8000
+error-background = #c86464
+keyword-background = #002240
+builtin-background = #002240
+break-background = #808000
+builtin-foreground = #ff00ff
+definition-foreground = #5e5eff
+stdout-foreground = #c2d1fa
+definition-background = #002240
+normal-foreground = #FFFFFF
+cursor-foreground = #ffffff
+stdout-background = #002240
+hit-foreground = #002240
+comment-background = #002240
+break-foreground = #FFFFFF
diff --git a/Lib/idlelib/configDialog.py b/Lib/idlelib/configDialog.py
index 4a759b4..f5a1c4b 100644
--- a/Lib/idlelib/configDialog.py
+++ b/Lib/idlelib/configDialog.py
@@ -524,6 +524,20 @@
 
     def VarChanged_builtinTheme(self, *params):
         value = self.builtinTheme.get()
+        if value == 'IDLE Dark':
+            tkMessageBox.showwarning(
+                title="The 'IDLE Dark' Text Color Theme",
+                message="IDLE Dark is new in October, 2015.  Trying to "
+                        "run earlier versions of IDLE with it selected "
+                        "will disable colorizing, or worse.\n\n"
+                        "If you might ever run an earlier release of IDLE, "
+                        "then before exiting this version, "
+                        "either switch to another theme or "
+                        "hit the 'Save as New Custom Theme' button.  "
+                        "The latter requires a new name, such as "
+                        "'Custom Dark', but the custom theme will work "
+                        "with any IDLE release, and can be modified.",
+                parent=self)
         self.AddChangedItem('main', 'Theme', 'name', value)
         self.PaintThemeSample()