One can easily change the background color of the TabHeader, but there is no easy way to change the Text (Foreground) color. The only do this, that I have seen, is to create (via code), custom tab header content (see bottom).
This actually bring up another issue / question: there does not appear to be a way to declare a tab header template. I would prefer to declare my header template in XAML and have it applied to each tab. Am I missing something?
var tab = new TabViewItem{ BindingContext = item.OriginalValue};var tabLayout = new StackLayout{ Spacing = 0, StyleClass = new[] { "SubTab" }};tabLayout.Children.Add(new Label(){ Text = item.Name, StyleClass = new[] { "SubTabItemText" }});tab.Header.Content = tabLayout;Tabs.Items.Add(tab);