diff --git a/voctogui/ui/voctogui.css b/voctogui/ui/voctogui.css
new file mode 100644
index 00000000..f1c59aa0
--- /dev/null
+++ b/voctogui/ui/voctogui.css
@@ -0,0 +1,11 @@
+.btn_grp_a:checked {
+  background-image: none;
+  background-color: blue;
+  color: white;
+}
+
+.btn_grp_b:checked {
+  background-image: none;
+  background-color: red;
+  color: white;
+}
\ No newline at end of file
diff --git a/voctogui/ui/voctogui.ui b/voctogui/ui/voctogui.ui
index 480acc9c..71ddf830 100644
--- a/voctogui/ui/voctogui.ui
+++ b/voctogui/ui/voctogui.ui
@@ -332,6 +332,9 @@
                     <property name="receives_default">True</property>
                     <property name="margin_right">5</property>
                     <property name="draw_indicator">False</property>
+                    <style>
+                      <class name="btn_grp_a"/>
+                    </style>
                   </object>
                   <packing>
                     <property name="expand">False</property>
@@ -349,6 +352,9 @@
                     <property name="receives_default">True</property>
                     <property name="margin_right">5</property>
                     <property name="draw_indicator">False</property>
+                    <style>
+                      <class name="btn_grp_b"/>
+                    </style>
                   </object>
                   <packing>
                     <property name="expand">False</property>
diff --git a/voctogui/voctogui.py b/voctogui/voctogui.py
index 429f4121..f20889a8 100755
--- a/voctogui/voctogui.py
+++ b/voctogui/voctogui.py
@@ -68,6 +68,36 @@ def __init__(self):
             raise Exception("Can't find any .ui-Files to use "
                             "(searched {})".format(', '.join(paths)))
 
+        #
+        # search for a .css style sheet file and load it
+        #
+
+        css_provider = Gtk.CssProvider()
+        context = Gtk.StyleContext()
+
+        css_paths = [
+            os.path.join(os.path.dirname(os.path.realpath(__file__)),
+                         'ui/voctogui.css'),
+            '/usr/lib/voctogui/ui/voctogui.css'
+        ]
+
+        for path in css_paths:
+            self.log.debug('trying to load css-file from file %s', path)
+
+            if os.path.isfile(path):
+                self.log.info('loading css-file from file %s', path)
+                css_provider.load_from_path(path)
+                break
+        else:
+            raise Exception("Can't find any .css-Files to use "
+                            "(searched {})".format(', '.join(css_paths)))
+
+        context.add_provider_for_screen(
+            Gdk.Screen.get_default(),
+            css_provider,
+            Gtk.STYLE_PROVIDER_PRIORITY_USER
+        )
+
         self.ui.setup()
 
     def run(self):