set colour JButton to opaque

git-svn-id: svn+ssh://svn.internal.sanger.ac.uk/repos/svn/pathsoft/artemis/trunk@9061 ee4ac58c-ac51-4696-9907-e4b3aa274f04

uk/ac/sanger/artemis/circular/GeneticMarker.java

@@ -323,6 +323,7 @@ public class GeneticMarker extends JPanel
     };
     button.setBackground(col);
     button.setBorderPainted(false);
+    button.setOpaque(true);
     button.setMargin(new Insets(0,0,0,0));
     Dimension d = new Dimension(25,25);
     button.setPreferredSize(d);