Using resources as conversion results in a bind converter

When I try to bind a valueconverter from a defined enum Status to brush, I get an error in my XAML designer:

'OKStatus' resource not found.

The application works fine runtime, but I'm not able to see my GUI in the designer. My resources are defined in the color.xaml file, which is read at run time. All code is within the same namespace

My XAML:

xmlns:config="clr-namespace:App.MyNamespace"

<UserControl.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="c:\Skins\Colors.xaml" />
            <ResourceDictionary Source="c:\Skins\Common.xaml" />                
        </ResourceDictionary.MergedDictionaries>
        <config:StatusConverter x:Key="StateConverter" />
        <config:BoolConverter x:Key="BoolConverter" />
        <config:BooleanConverter x:Key="BooleanConverter" />
    </ResourceDictionary>
</UserControl.Resources>

and

Status

My converter:

[ValueConversion(typeof(bool), typeof(Brush))]
public class BoolConverter : IValueConverter
{
    public object Convert(object value, Type targetType,
        object parameter, CultureInfo culture)
    {
        bool state = (bool)value;

        FrameworkElement FrameElem = new FrameworkElement();

        if (state == true)
            return (FrameElem.FindResource("OKStatus") as Brush);
        else
            return (FrameElem.FindResource("ErrorStatus") as Brush);
    }

    public object ConvertBack(object value, Type targetType,
        object parameter, CultureInfo culture)
    {
        return null;
    }
}

In this code the frameElem wont have any knowledge of the resources I have defined I guess, so I need a way to get access to my resources during design. Is this possible?

Actually what I ended up doing (for now) was to change from FindResource to TryFindResource, and put the statements in a try/catch block. This seems to work so far.

try
{
    if (state == true)
       return (FrameElem.TryFindResource("OKStatus") as Brush);
    else
       return (FrameElem.TryFindResource("ErrorStatus") as Brush);
}

catch (ResourceReferenceKeyNotFoundException)
{
   return new SolidColorBrush(Colors.LightGray);
}