3074/App.xaml

<Application x:Class="tsf_3074.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:tsf_3074"
             Startup="App_OnStartup"
             DispatcherUnhandledException="App_OnDispatcherUnhandledException">
    <Application.Resources>
        <ResourceDictionary>
            <Style TargetType="TextBlock">
                <Style.Triggers>
                    <Trigger Property="TextBlock.Text" Value="On">
                        <Setter Property="Foreground" Value="LawnGreen"></Setter>
                    </Trigger>
                    <Trigger Property="TextBlock.Text" Value="Off">
                        <Setter Property="Foreground" Value="Red"></Setter>
                    </Trigger>
                </Style.Triggers>
            </Style>
        </ResourceDictionary>
    </Application.Resources>
</Application>