After modifying the Login Logo or Background Color, or first time users will only see the 'Clarity' logo and default color till they log in.
If you change Clarity Branding or if you delete browser cache, it takes a full login to the system for all users to see your new logo.
This is working as designed. When you modify the Login Logo/Background Color, users will need to login once first to pick up the configuration, which then gets cached in the browser and will display the custom logo with each subsequent login.