Customize Dynamics 365 Mobile App

Hello everyone 

I have a customer who uses the mobile app, but a couple of users use the mobile app for both Production and QA environment. They want to be able to easily distinguish the site they are on by have a different colors when they visit any QA app. 

For the web version, we changed the Theme, but I did not see anything similar for the mobile app. It doesn't matter if Dynamics for 365 or Dynamics for Sales or Power App. 

Any ideas or solutions? 

Thanks .