Skinning of native xamarin apps

Hi guys. Has has anybody had to build a native app with different themes. How would you do that with out duplicating the code base. So for example if i have to build an app for a bank in one country and use that same app for a bank in a different country, the android and ios apps should function the same but will just have to be branded differently for each company. I would need then need the same app multiple times in the app stores but branded for each company. Is this possible to do?
Thank you