Thank you for sharing your code sample. I see that the Foreground of the ProgressBar is White. Change the color to Blue for instance or remove it, so it could take the default color. Then you will be able to see color of the progress bar in InDeterminate mode.
Telerik by Progress
Want to extend the target reach of your WPF applications, leveraging iOS, Android, and UWP? Try UI for Xamarin
, a suite of polished and feature-rich components for the Xamarin framework, which allow you to write beautiful native mobile apps using a single shared C# codebase.