Index: trunk/src/org/openstreetmap/josm/tools/ColorHelper.java
===================================================================
--- trunk/src/org/openstreetmap/josm/tools/ColorHelper.java	(revision 9228)
+++ trunk/src/org/openstreetmap/josm/tools/ColorHelper.java	(revision 9229)
@@ -82,6 +82,7 @@
     public static Color getForegroundColor(Color bg) {
         // http://stackoverflow.com/a/3943023/2257172
-        return (bg.getRed()*0.299 + bg.getGreen()*0.587 + bg.getBlue()*0.114) > 186 ?
-                Color.BLACK : Color.WHITE;
+        return bg == null ? null :
+              (bg.getRed()*0.299 + bg.getGreen()*0.587 + bg.getBlue()*0.114) > 186 ?
+                  Color.BLACK : Color.WHITE;
     }
 }
Index: trunk/test/unit/org/openstreetmap/josm/tools/ColorHelperTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/tools/ColorHelperTest.java	(revision 9229)
+++ trunk/test/unit/org/openstreetmap/josm/tools/ColorHelperTest.java	(revision 9229)
@@ -0,0 +1,28 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.tools;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import java.awt.Color;
+
+import org.junit.Test;
+
+/**
+ * Unit tests for class {@link ColorHelper}.
+ */
+public class ColorHelperTest {
+
+    /**
+     * Unit test of method {@link ColorHelper#getForegroundColor}.
+     */
+    @Test
+    public void testGetForegroundColor() {
+        assertNull(ColorHelper.getForegroundColor(null));
+        assertEquals(Color.WHITE, ColorHelper.getForegroundColor(Color.BLACK));
+        assertEquals(Color.WHITE, ColorHelper.getForegroundColor(Color.DARK_GRAY));
+        assertEquals(Color.BLACK, ColorHelper.getForegroundColor(Color.LIGHT_GRAY));
+        assertEquals(Color.BLACK, ColorHelper.getForegroundColor(Color.YELLOW));
+        assertEquals(Color.BLACK, ColorHelper.getForegroundColor(Color.WHITE));
+    }
+}