Hey, OP’s question is resolved due to the CSS being managed by the accent settings, but, how do I override the CSS of portal elements?
For some reason, I’m also getting the behavior of CSS overriding working elsewhere but not in the signup portal. In my case, I want my blog to be subscribe only (and no sign in). So, I applied display: none to .gh-portal-signup-message in order to hide the “Already a member? Sign in” text in the official Journal theme. Not working.
Yeah unfortunately Ghost CMS does a really poor job of actually opening up all areas of the site for customisation in regards to design. This is especially problematic of the portal. The fact they’re at version 5 and this still isn’t done is absolutely mind-boggling.
I have a dark mode theme I’m using and the portal is such a shocking change, and completely destroys branding. Awful experience.
The Portal code runs in an iframe. You can’t easily restyle it with css. If you’re self hosted, you can load a custom version of the portal that’s styled as you want it. (Not an option on Ghost Pro and other managed hosts.)
However, you /can/ turn it off. Many themes offer custom sign-in/sign-up pages, that run on the theme level and /can/ be customized. For example, Liebling has a custom newsletter sign-up: https://liebling.eduardogomez.io/ (free theme!). Many of @fueko 's themes (not free) include custom membership pages, such as this one: https://eihei-dark.fueko.net/ (click the join button)
Not disagreeing that there should be an easy way to tweak the display of Portal, but there are some options, at least.
Since this thread got bumped: Magic Pages hosters can load a separate version of portal via their admin panel. Ghost pro hosters can edit the theme - use the exclude argument to ghost_head to not auto-load portal and then load custom portal within the theme.