...
Portal Appearance provides a way in which the user may choose the color in which Portal will open.
After a color is selected from the Colors drop-down list, click on Save Changes to apply the current setting for all users of the current tenant. If you have multiple tenants you can set a different color for each of them.
No restart is required in order the chosen color to be applied.
Go To Portal Custom Design
The user can customize all colors on the Portal per Tenant.