Index: trunk/src/org/openstreetmap/josm/gui/tagging/presets/items/Combo.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/tagging/presets/items/Combo.java	(revision 16293)
+++ trunk/src/org/openstreetmap/josm/gui/tagging/presets/items/Combo.java	(revision 16294)
@@ -104,4 +104,5 @@
             p.add(combobox, GBC.std().fill(GBC.HORIZONTAL));
             JButton button = new JButton(new ChooseColorAction());
+            button.setBorderPainted(false);
             p.add(button, GBC.eol().fill(GBC.VERTICAL));
             ActionListener updateColor = ignore -> button.setBackground(getColor());