Binding TextBlock foreground to Global.cs variable in xaml - xaml

Question

I've been trawling the web trying to find a similar problem but can't find anything that solves my problem.
I have a static class holding global variables, some of these are colour variables which I want to be able to bind in my xaml controls such that I only have to change one variable to change the lot (the reason for global variables).
The class namespace is MyApp.Assets.Resources the class name is Global(.cs).
In my class I have variables named DEFAULTCOLOR, OKCOLOR and ALARMCOLOR.
My xaml:
<UserControl
<!-- ... -->
xmlns:custom="clr-namespace:InspectionDB.Assets.Resources"
>
<UserControl.Resources>
<custom:Global x:Name="global"/> <!-- THIS GIVES AN ERROR SEE BELOW-->
<common:HierarchicalDataTemplate x:Key="Level1" ItemsSource="{Binding Path=Children}">
<StackPanel Orientation="Horizontal">
<Image Source="{Binding Type, Converter={StaticResource localTreeImgConverter}}"/>
<TextBlock {Binding...} />
<StackPanel Orientation="Horizontal" Visibility="{Binding Type, Converter={StaticResource localStatusVisibilityConverter}}">
<TextBlock Margin="5,0, 0,0" Text="[ " Foreground="{Binding DEFAULTCOLOR, Source={StaticResource global}}" />
<TextBlock Text="{Binding Critical}" Foreground="{Binding ALARMCOLOR, Source={StaticResource global}}"/>
<TextBlock Text=" | " Foreground="{Binding DEFAULTCOLOR, Source={StaticResource global}}"/>
<TextBlock Text="{Binding OK}" Foreground="{Binding OKCOLOR, Source={StaticResource global}}"/>
<TextBlock Text=" ]" Foreground="{Binding DEFAULTCOLOR, Source={StaticResource global}}"/>
</StackPanel>
</StackPanel>
</common:HierarchicalDataTemplate>
</UserControl.Resources>
<Grid>
<!-- Where the hierarchical template is used -->
</Grid>
</UserControl>
The part in the Resources throws an error as well as the binding:
Unable to cast object of type 'ApplicationProxy' to type 'Microsoft.Expression.DesignModel.DocumentModel.DocumentNode'.
What is wrong with my code and how can I get it to work?

Answer 1

I found what my problem was, and therefore why I couldn't find any similar situation.
I had public class Global : App - don't ask me why, I'm sure there was a valid reason long ago but it meant it had some kind of funky circular referencing going on.
Problem solved.