When you create your Ouvvi environment you may wish to customise your instances so that they can be easily recognisable at a glance.
This may be done to distinguish between DEV/PROD/UAT environments, so that users work on the correct environment.
To change the colour of the instance go to Settings
> System Settings
> Visual UI Theme
and then select the theme you wish to apply from the drop down.
Then to save your changes scroll to the bottom of the page and click Save
.