Hi Morgan,
Thanks for your patience.
From your update we understand that you want to use keys to fill your Rectangle like Xamarin.Forms. We need to check the feasibility to show the keys for all the controls like Xamarin.Forms since we have nearly 150 controls in WPF platform.
In the Meantime, we have provided the solution of this requirement.
To get the keys for different controls while using specific theme you can use export theme option. While exporting the theme the keys for all controls added in Brushes.Xaml file(located in Common Folder).In this file we have added the keys for all the controls for exported theme. You can set the keys dynamically for Rectangle. Please refer the below help documentation to export the theme.
As of now we understand that you want to fill RibbonBar key color in your Rectangle. For this first you need to set the theme in your project. Please refer the below screen shot for keys of Ribbon control for syncfusion themes. Also, we have shared the excel file which we have maintain internally to map the keys for Ribbon control.
Screen shot for key of Ribbon
In the below file left side we have added the keys name for Ribbon control
Output:
Please try it with the above solution and let us know if you have any clarification on this solution. If you have not clear with this solution, we request you to arrange a web meeting to clearly explain this solution. Can you to provide your availability time. So, that we can check and arrange the meeting accordingly.
Regards,
Elakkiya