<Window x:Class="WpfAppExamples.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="RadioButtonSample" Height="150" Width="250">
    <Window.Resources>
        <Style TargetType="RadioButton" BasedOn="{StaticResource {x:Type RadioButton}}">
            <Style.Triggers>
                <Trigger Property="IsChecked" Value="False">
                    <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                </Trigger>
            </Style.Triggers>
        </Style>
    </Window.Resources>
    <StackPanel Margin="10">
        <Label FontWeight="Bold">Are you ready?</Label>
        <RadioButton GroupName="testing">Yes</RadioButton>
        <RadioButton GroupName="testing">No</RadioButton>
        <RadioButton IsChecked="True" GroupName="testing">Maybe</RadioButton>
    </StackPanel>
</Window>