The subscription and unsubscription (using the variable $unsubUrl$) form provided by Splio Platform have a default template for all customers, but it is possible to create your own design.
First you will need to create and host a CSS file, then put the External stylesheet URL in the platform (Admin > Subscription Form.)
Note: The server must use https authentication, otherwise the unsubscription form will empty all css styles.
Subscription form (before customization)
Subscription form (after customization)
Unsubscription form (before customization)
Unsubscription form (after customization)
Read the dedicated page for more information about variables.