To fully use themes in model driven apps, you currently need to:

1. Create an XML file with Hex codes and edit the "Override app header color" setting, and
2. Go to Settings -> Customization -> Customizations -> Theme and update the Hex codes and Logo with another web resource

We should combine these two locations and make it simpler to update the colors vs. the manual steps of creating web resources and updating in different spots. Sync these two theming locations into one.