How to do you change the color of the "underline" marking the selected tab on a TabbedPage in Xamarin.Forms?

Question

I'm currently adding several different themes (10-ish) to a Xamarin.Forms app. I've figured out how to dynamically change the color of everything except the "underline" on a tab on TabbedPage (see the attached image).

Screenshot identifying the TabbedPage "underline" with a red rectangle

I've tried to set the five different color properties (that I know of) on the TabbedPage as well as the BackgroundColor on the ContentPages in the tabs:

TabbedPage tabbedPage = new TabbedPage { Title = "Tabbed Page" };

tabbedPage.BarBackgroundColor = Color.Black;
tabbedPage.BarTextColor = Color.Gray;
tabbedPage.SelectedTabColor = Color.Black;
tabbedPage.UnselectedTabColor = Color.Black;

tabbedPage.BackgroundColor = Color.Black;

tabbedPage.Children.Add(new ContentPage { Title = "Page 1", BackgroundColor = Color.Gray });
tabbedPage.Children.Add(new ContentPage { Title = "Page 2", BackgroundColor = Color.Gray });

await Application.Current.MainPage.Navigation.PushAsync(tabbedPage);

Is it possible to set the color of the "underline" in Xamarin.Forms? Or do I need to make platform-specific changes to achieve this?