diff --git a/hgext/color.py b/hgext/color.py
--- a/hgext/color.py
+++ b/hgext/color.py
@@ -296,18 +296,12 @@ def _modesetup(ui, coloropt):
         return realmode
     return None
 
-class colorui(uimod.ui):
-    pass
-
 def uisetup(ui):
     if ui.plain():
         return
-    if not isinstance(ui, colorui):
-        colorui.__bases__ = (ui.__class__,)
-        ui.__class__ = colorui
     def colorcmd(orig, ui_, opts, cmd, cmdfunc):
         mode = _modesetup(ui_, opts['color'])
-        colorui._colormode = mode
+        uimod.ui._colormode = mode
         if mode and mode != 'debug':
             color.configstyles(ui_)
         return orig(ui_, opts, cmd, cmdfunc)
diff --git a/tests/test-ui-color.py b/tests/test-ui-color.py
--- a/tests/test-ui-color.py
+++ b/tests/test-ui-color.py
@@ -1,16 +1,13 @@
 from __future__ import absolute_import, print_function
 
 import os
-from hgext import (
-    color,
-)
 from mercurial import (
     dispatch,
     ui as uimod,
 )
 
 # ensure errors aren't buffered
-testui = color.colorui()
+testui = uimod.ui()
 testui.pushbuffer()
 testui.write(('buffered\n'))
 testui.warn(('warning\n'))
@@ -35,6 +32,7 @@ def runcmd():
     dispatch.dispatch(dispatch.request(['version', '-q'], ui_))
 
 runcmd()
-print("colored? " + str(issubclass(ui_.__class__, color.colorui)))
+print("colored? %s" % (ui_._colormode is not None))
 runcmd()
-print("colored? " + str(issubclass(ui_.__class__, color.colorui)))
+print("colored? %s" % (ui_._colormode is not None))
+