diff --git a/tests/run-tests.py b/tests/run-tests.py
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -416,12 +416,12 @@
         parser.error('--chg does not work when --with-hg is specified '
                      '(use --with-chg instead)')
 
-    global with_color
-    if options.color != 'auto':
-        if options.color == 'never':
-            with_color = False
-        else: # 'always', for testing purposes
-            with_color = True
+    if options.color == 'auto':
+        options.color = with_color
+    elif options.color == 'never':
+        options.color = False
+    else: # 'always', for testing purposes
+        options.color = True
 
     global useipv6
     if options.ipv6:
@@ -1651,7 +1651,7 @@
                 else:
                     self.stream.write('\n')
                     for line in lines:
-                        if with_color and pygmentspresent:
+                        if self._options.color and pygmentspresent:
                             line = pygments.highlight(
                                     line,
                                     lexers.DiffLexer(),