The Office themes are located in the ThemePack assemblies (Xceed.Wpf.DataGrid.ThemePack.[#].dll), which must be included in your references. You can then apply them to the grid by setting the View.Theme property using property element syntax:

<Grid xmlns:xcdg="http://schemas.xceed.com/wpf/xaml/datagrid">
  <Grid.Resources>
    <xcdg:DataGridCollectionViewSource x:Key="cvs_orders"
                                     Source="{Binding Source={x:Static Application.Current},
                                                      Path=Orders}"/>
  </Grid.Resources>
   <xcdg:DataGridControl x:Name="OrdersGrid"
                         ItemsSource="{Binding Source={StaticResource cvs_orders}}">

     <xcdg:DataGridControl.View>
        <xcdg:CardView>
           <xcdg:CardView.Theme>
              <xcdg:Office2007BlueTheme/>
           </xcdg:CardView.Theme>
        </xcdg:CardView>
     </xcdg:DataGridControl.View>
   </xcdg:DataGridControl>
</Grid>

You can look in the documentation under Basic Concepts\Appearance\Views and Themes for a list of the theme names. Also note that the themes located in the theme packs require a Pro license key (either trial or registered).