diff --git a/mercurial/color.py b/mercurial/color.py
--- a/mercurial/color.py
+++ b/mercurial/color.py
@@ -183,7 +183,7 @@ def setup(ui):
 def _modesetup(ui):
     if ui.plain():
         return None
-    config = ui.config('ui', 'color', 'auto')
+    config = ui.config('ui', 'color')
     if config == 'debug':
         return 'debug'
 
diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -430,6 +430,9 @@ coreconfigitem('ui', 'clonebundleprefers
 coreconfigitem('ui', 'clonebundles',
     default=True,
 )
+coreconfigitem('ui', 'color',
+    default='auto',
+)
 coreconfigitem('ui', 'commitsubrepos',
     default=False,
 )