The branding option of the admin management UI allows for custom CSS to be entered for specific objects in the user console UI.
Sometimes these are not applied and seem not to work.
Identity Portal 14.0 andup
Usually, this is due to a conflict in the CSS on the page the user is accessing.
In order to make sure your customization is applied, add the string '!important' to the string.
For example, change the color of ' ffffff ' to ' ffffffff !important'