How to change CSS for Signup portal of Subscribe?

I would like to change CSS for some of the components in the signup/login popup so it matches with my dark theme.

image

I tried code injection, but it is not working. How can I change it?

     .gh-portal-btn-link{
    	color: #ee7169 !important;
    }

    .gh-portal-btn{
        background-color: #5e5e9a !important;
    }

I think that’s controlled by the accent color you have in brand settings