While “dynamically overriding resources” might seem the straightforward solution to your problem, I believe a cleaner approach would be to use the official data binding implementation https://developer.android.com/tools/data-binding/guide.html since it doesn’t imply hacking the android way.
You could pass your branding settings using a POJO. Instead of using static styles like @color/button_color you could write @{brandingConfig.buttonColor} and bind your views with the desired values. With a proper activity hierarchy, it shouldn’t add too much boilerplate.
This also gives you the ability to change more complex elements on your layout, i.e.: including different layouts on other layout depending on the branding settings, making your UI highly configurable without too much effort.