修改下aa的事件<Style x:Key="aa" TargetType="Control">
        <Setter Property="Background" Value="Wheat"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="Control">
                    <Grid Background="{TemplateBinding Background}" Name="gd">
                        <TextBlock Text="汤姆" Background="Wheat"/>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>绑定Background,然后对UserControl进行 MouseDown 的事件处理吧,修改Background属性就可以~