OnlineMonitorSystem/HandyControl/HandyControl_Shared/Themes/Styles/ElementGroup.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:hc="clr-namespace:HandyControl.Controls">

    <Style BasedOn="{StaticResource ElementGroupBaseStyle}" TargetType="hc:ElementGroup"/>

    <Style x:Key="ElementGroupSolid" BasedOn="{StaticResource ElementGroupBaseStyle}" TargetType="hc:ElementGroup">
        <Setter Property="hc:VisualElement.HighlightBorderBrush" Value="{DynamicResource TitleBrush}"/>
        <Setter Property="hc:VisualElement.HighlightBackground" Value="{DynamicResource TitleBrush}"/>
        <Setter Property="hc:VisualElement.HighlightForeground" Value="{DynamicResource TextIconBrush}"/>
    </Style>

</ResourceDictionary>