Current implementation of Theme Color is annoying.

1. Setting the ThemeColor to be a static class instead of an ENum is bizarre.  It makes it really annoying to pass a typed themeColor into an input parameter.  I can understand the want to be more flexible and the inputs to your controls being a string
2. You are re-using the ThemeColor in several different places where it is simply repeated. This makes things really annoying.  

I recommend:

1. Keeping the inputs to your controls for theme colors to be a string, so you can maintain the flexiblity (reason I assume you changed this in the first place)
2. Use a single enum and in the documentation / examples say by default use "nameof(ThemeColor.Primary) for default themes"  You can add your own custom theme by .... and pass in a string.