--- a/hgext/color.py	Sun Aug 24 17:35:36 2014 -0400
+++ b/hgext/color.py	Sun Aug 24 17:40:27 2014 -0400
@@ -27,6 +27,13 @@
 effects. This includes the special "none" effect, which nullifies
 other effects.
 
+Labels are normally invisible. In order to see these labels and their
+position in the text, use the global --color=debug option. In case of
+multiple labels for the same text, the labels will be enclosed by
+square brackets, e.g.
+
+  [log.changeset changeset.secret](changeset:   22611:6f0a53c8f587)
+
 The following are the default effects for some default labels. Default
 effects may be overridden from your configuration file::
 
@@ -177,6 +184,9 @@
 def _modesetup(ui, coloropt):
     global _terminfo_params
 
+    if coloropt == 'debug':
+        return 'debug'
+
     auto = (coloropt == 'auto')
     always = not auto and util.parsebool(coloropt)
     if not always and not auto:
@@ -387,10 +397,24 @@
             return super(colorui, self).write_err(
                 *[self.label(str(a), label) for a in args], **opts)
 
+    def showlabel(self, msg, label):
+        if ' ' in label:
+            label = '[' + label + ']'
+        if label:
+            if msg and msg[-1] == '\n':
+                return "%s(%s)\n" % (label, msg[:-1])
+            else:
+                return "%s(%s)" % (label, msg)
+        else:
+            return msg
+
     def label(self, msg, label):
         if self._colormode is None:
             return super(colorui, self).label(msg, label)
 
+        if self._colormode == 'debug':
+            return self.showlabel(msg, label)
+
         effects = []
         for l in label.split():
             s = _styles.get(l, '')
@@ -436,7 +460,7 @@
     def colorcmd(orig, ui_, opts, cmd, cmdfunc):
         mode = _modesetup(ui_, opts['color'])
         colorui._colormode = mode
-        if mode:
+        if mode and mode != 'debug':
             extstyles()
             configstyles(ui_)
         return orig(ui_, opts, cmd, cmdfunc)
@@ -446,9 +470,9 @@
 def extsetup(ui):
     commands.globalopts.append(
         ('', 'color', 'auto',
-         # i18n: 'always', 'auto', and 'never' are keywords and should
-         # not be translated
-         _("when to colorize (boolean, always, auto, or never)"),
+         # i18n: 'always', 'auto', 'never', and 'debug' are keywords
+         # and should not be translated
+         _("when to colorize (boolean, always, auto, never, or debug)"),
          _('TYPE')))
 
 @command('debugcolor', [], 'hg debugcolor')