あなたは、スタイルのサンプルコードは
<Border x:Name="UnderlayBorder" Background="{Binding MouseOverBackground, RelativeSource={RelativeSource TemplatedParent}}" Opacity="0.5" Visibility="Collapsed"/>
<Custom:RibbonToggleButton x:Name="PART_ToggleButton" BorderBrush="{TemplateBinding BorderBrush}" Background="Transparent" ToolTipService.BetweenShowDelay="0" CheckedBackground="{TemplateBinding CheckedBackground}" ClickMode="Press" CornerRadius="0,2,2,0" CheckedBorderBrush="{TemplateBinding CheckedBorderBrush}" FocusedBackground="{TemplateBinding FocusedBackground}" FocusedBorderBrush="{TemplateBinding FocusedBorderBrush}" FocusVisualStyle="{x:Null}" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" ToolTipService.InitialShowDelay="900" IsChecked="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" Label="{TemplateBinding Label}" MouseOverBackground="{TemplateBinding MouseOverBackground}" MouseOverBorderBrush="{TemplateBinding MouseOverBorderBrush}" PressedBorderBrush="{TemplateBinding PressedBorderBrush}" Padding="{TemplateBinding Padding}" PressedBackground="{TemplateBinding PressedBackground}" Custom:RibbonTwoLineText.PathData="M0,0L2.5,3 5,0z" Style="{x:Null}" ToolTipService.ShowDuration="20000" ToolTipDescription="{TemplateBinding DropDownToolTipDescription}" ToolTipFooterDescription="{TemplateBinding DropDownToolTipFooterDescription}" ToolTipImageSource="{TemplateBinding DropDownToolTipImageSource}" ToolTipFooterTitle="{TemplateBinding DropDownToolTipFooterTitle}" ToolTipFooterImageSource="{TemplateBinding DropDownToolTipFooterImageSource}" ToolTipTitle="{TemplateBinding DropDownToolTipTitle}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}">
<Custom:RibbonToggleButton.ControlSizeDefinition>
<Custom:RibbonControlSizeDefinition IsLabelVisible="False" ImageSize="Collapsed"/>
</Custom:RibbonToggleButton.ControlSizeDefinition>
<Custom:RibbonToggleButton.Template>
<ControlTemplate TargetType="{x:Type Custom:RibbonToggleButton}">
<Grid x:Name="MainGrid" SnapsToDevicePixels="True">
<Border x:Name="OuterBorder" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" CornerRadius="{TemplateBinding CornerRadius}"/>
<Border x:Name="MiddleBorder" BorderBrush="Transparent" BorderThickness="{TemplateBinding BorderThickness}" Background="Transparent" CornerRadius="{TemplateBinding CornerRadius}">
<Border x:Name="InnerBorder" BorderBrush="Transparent" BorderThickness="{TemplateBinding BorderThickness}" Background="Transparent" CornerRadius="{TemplateBinding CornerRadius}" Padding="{TemplateBinding Padding}">
<StackPanel x:Name="StackPanel" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}">
<Image x:Name="PART_Image" RenderOptions.BitmapScalingMode="NearestNeighbor" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Height="32" Margin="{DynamicResource {ComponentResourceKey ResourceId=LargeImageMargin, TypeInTargetAssembly={x:Type Custom:Ribbon}}}" Source="{TemplateBinding LargeImageSource}" VerticalAlignment="Center" Width="32"/>
<Grid x:Name="Grid" HorizontalAlignment="Left" VerticalAlignment="Top" >
<Custom:RibbonTwoLineText x:Name="TwoLineText" Custom:RibbonTwoLineText.HasTwoLines="{TemplateBinding Custom:RibbonTwoLineText.HasTwoLines}" HorizontalAlignment="Center" LineStackingStrategy="BlockLineHeight" LineHeight="5" Margin="1,1,1,0" PathFill="{TemplateBinding Foreground}" Custom:RibbonTwoLineText.PathData="{TemplateBinding Custom:RibbonTwoLineText.PathData}" TextAlignment="Center" Text="{TemplateBinding Label}" VerticalAlignment="Top"/>
</Grid>
</StackPanel>
</Border>
</Border>
</Grid>
ある part_toggleボタンのスタイルを変更することにより、リボン分割ボタンにトグルボタンのスタイルを変更することができます