<Page
  …
  xmlns:igWindows="http://infragistics.com/Windows"
  …>
  <Page.Resources>
    <ResourceDictionary>
      <Style TargetType="{x:Type igWindows:ExpansionIndicator}">
        <Setter Property="Template">
          <Setter.Value>
            <ControlTemplate TargetType="{x:Type igWindows:ExpansionIndicator}">
              <Grid>
                <Path
                  x:Name="ArrowPath"
                  Width="10"
                  Height="10"
                  Stretch="Fill"
                  Stroke="#FF00FF00"
                  StrokeThickness="1"
                  Fill="{Binding RelativeSource={RelativeSource Self}, Path=Stroke, Mode=OneWay}"
                  Data="M8,5 L8,14 L14,9.5 z"
                  Visibility="Visible" />
              </Grid>
              <ControlTemplate.Triggers>
                <Trigger Property="IsChecked" Value="True">
                  <Trigger.Setters>
                    <Setter TargetName="ArrowPath" Property="Stroke" Value="#FFFF0000" />
                    <Setter TargetName="ArrowPath" Property="RenderTransform">
                      <Setter.Value>
                        <RotateTransform CenterX="5" CenterY="5" Angle="90" />
                      </Setter.Value>
                    </Setter>
                  </Trigger.Setters>
                </Trigger>
                <Trigger Property="IsMouseOver" Value="True">
                  <Trigger.Setters>
                    <Setter TargetName="ArrowPath" Property="Stroke" Value="#FFFFFF00"/>
                    <Setter TargetName="ArrowPath" Property="Cursor" Value="Hand"/>
                  </Trigger.Setters>
                </Trigger>
              </ControlTemplate.Triggers>
            </ControlTemplate>
          </Setter.Value>
        </Setter>
      </Style>
    </ResourceDictionary>
  </Page.Resources>
  …
</Page>