diff --git a/contrib/python3-whitelist b/contrib/python3-whitelist
--- a/contrib/python3-whitelist
+++ b/contrib/python3-whitelist
@@ -534,6 +534,7 @@
 test-ssh.t
 test-sshserver.py
 test-stack.t
+test-status-color.t
 test-status-inprocess.py
 test-status-rev.t
 test-status-terse.t
diff --git a/mercurial/color.py b/mercurial/color.py
--- a/mercurial/color.py
+++ b/mercurial/color.py
@@ -296,9 +296,9 @@
                 if valideffect(ui, e):
                     good.append(e)
                 else:
-                    ui.warn(_("ignoring unknown color/effect %r "
+                    ui.warn(_("ignoring unknown color/effect %s "
                               "(configured in color.%s)\n")
-                            % (e, status))
+                            % (stringutil.pprint(e), status))
             ui._styles[status] = ' '.join(good)
 
 def _activeeffects(ui):