Converter for changing Textblock Foreground

Hello Everybody !!

I need to change dynamically the foreground of a textblock.

I developed a converter :

 public class BooleanToColorConverter : IValueConverter
  {

    public object Convert(object value, Type targetType, object parameter, string language)
    {
      if (value != null)
      {
        bool val = (bool)value;
        if (parameter != null && string.Compare(parameter as string, "calendar", StringComparison.CurrentCultureIgnoreCase) == 0)
        {
          return val == true ? new SolidColorBrush(Color.FromArgb(0, 255, 0, 0)) : new SolidColorBrush(Color.FromArgb(0, 140,140,140));
        }
      
      }
      return false;
    }

    public object ConvertBack(object value, Type targetType, object parameter, string language)
    {
      throw new NotImplementedException();
    }
  }

And this is my XAML Code :

                <TextBlock TextWrapping="Wrap" Grid.Column="1"
                           Foreground="{Binding IsWriteInRed, Converter={StaticResource BooleanToColorConverter}, ConverterParameter=calendar}" 
                           SelectionHighlightColor="{StaticResource WhiteSolidColorBrush}" Margin="5,0" VerticalAlignment="Center">
                  <Run Text="{Binding Company.Name}"/>
                  <Run Text=":"/>
                  <Run Text="{Binding Subject}"/>
                </TextBlock>

It doesn't work, I don't know why...any ideas please??

Thanks