My Domain Authentication Configuration (Logo and Background Color) Carries Over When Refreshing a Salesforce Sandbox.

If the pre-refresh sandbox has settings for Logo File and Background Color in the Authentication Settings section of My Domain, those settings will be carried over when the sandbox is refreshed.

To reset the Logo File and Background Color to default in the refreshed Sandbox, follow these steps:

1. Click [Setup]. 
2. In Lightning Experience, access to [Company Settings]|[My Domain]. In Salesforce Classic, access to [Domain Management]|[My Domain]. 
3. Go to the Authentication Configuration section on the My Domain page and click [Edit]. 
4. Click [Reset to Default].