import ScrollableTabView from 'react-native-scrollable-tab-view';
import SimpleTabBar from './DirYouPlacedThisIn/SimpleTabBar.js';

...

render() {
    return (
       <ScrollableTabView
          renderTabBar={() => <SimpleTabBar activeBackgroundColor="#f1c40f" />}
       >
        ...
      </ScrollableTabView>
    );
  }