The appearance of Minter.io can be set to either Light or Dark mode in your account settings, found here: https://minter.io/app/edit/appearance. By default the appearance is based on your current system settings.
You can also find this settings area by following these steps:
1. Click your account name in the top right of your report.
2. Choose 'Appearance'.
3. Choose the mode you would like to use.