SAML2 Login Dark mode

Problem Statement

It would be great to have a Dark mode for this screen, as it is a jarring experience for users using Dark mode.

Solution Brainstorm

As a test you can inject this chrome snippet to see what it could look like

const style = document.createElement('style');
style.textContent = `
@media (prefers-color-scheme: dark) {
  body.auth {
    background: #24202b;
    color: #e9e5eb;
  }

  body.auth a {
    color: #a396e8;
  }

  body.auth .pattern-bg {
    background-color: #24202b;
    opacity: 0.1;
  }

  body.auth .box {
    background: #2f2937;
    border-color: #453e4f;
    box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.4);
  }

  body.auth .box .box-header {
    background: #39323f;
    color: #e9e5eb;
    border-bottom-color: #453e4f;
  }

  body.auth .auth-container.border-bottom {
    border-bottom-color: #453e4f;
  }

  body.auth .auth-provider-column {
    border-left-color: #453e4f;
  }

  body.auth .auth-container .help-center-link {
    color: #a396e8;
  }

  body.auth .auth-footer .secondary {
    color: #b5b0bd;
  }

  body.auth .auth-footer .secondary:hover {
    color: #e9e5eb;
  }

  body.auth .nav-tabs > li > a {
    color: #b5b0bd;
  }

  body.auth .nav-tabs > li > a:hover,
  body.auth .nav-tabs > li > a:active,
  body.auth .nav-tabs > li > a:focus {
    color: #e9e5eb;
  }

  body.auth .nav-tabs > li.active a,
  body.auth .nav-tabs > li.active a:hover,
  body.auth .nav-tabs > li.active a:focus {
    color: #e9e5eb;
  }

  body.auth .form-control {
    background: #24202b;
    border-color: #453e4f;
    color: #e9e5eb;
    box-shadow: inset 0 2px 0 rgba(0, 0, 0, 0.12);
  }

  body.auth .form-control::placeholder {
    color: #b5b0bd;
  }

  body.auth .form-control:focus {
    border-color: #6c5fc7;
    box-shadow: inset 0 2px 0 rgba(0, 0, 0, 0.12), 0 0 6px rgba(108, 95, 199, 0.5);
  }

  body.auth .form-control:-webkit-autofill,
  body.auth .form-control:-webkit-autofill:hover,
  body.auth .form-control:-webkit-autofill:focus {
    -webkit-text-fill-color: #e9e5eb;
    box-shadow: inset 0 0 0 1000px #24202b;
    caret-color: #e9e5eb;
  }

  body.auth .help-block {
    color: #b5b0bd;
  }

  body.auth .btn-default {
    color: #e9e5eb;
    background: #39323f;
    border-color: #453e4f;
  }

  body.auth .btn-default:hover {
    color: #e9e5eb;
    background: #413a48;
    border-color: #51495d;
  }

  body.auth .btn-default:hover:active,
  body.auth .btn-default:focus,
  body.auth .btn-default:active,
  body.auth .btn-default.active,
  body.auth .btn-default.active:hover {
    color: #e9e5eb;
    background: #342e3a;
    border-color: #51495d;
  }

  body.auth .provider-logo.github,
  body.auth .provider-logo.rippling {
    filter: invert(1);
  }

  body.auth .alert-danger {
    background: #3b2733;
    border-color: #6b3a44;
    color: #f3b0b5;
  }

  body.auth .error,
  body.auth .has-error .help-block,
  body.auth .has-error .control-label {
    color: #f3b0b5;
  }

  body.auth .has-error .form-control {
    border-color: #6b3a44;
  }

  body.auth .has-error .form-control:focus {
    border-color: #6b3a44;
  }
}
`;
document.head.appendChild(style);

To make this permanent

static/less/auth.less

/**
* Auth Dark Mode
* ============================================================================
* These pages are rendered by Django rather than the React app, so the body
* never gets a `.theme-*` class to key off of. Visitors are also usually signed
* out, meaning there is no stored theme preference to read. Follow the OS
* setting instead.
*/

@auth-dark-bg: #24202b;
@auth-dark-surface: #2f2937;
@auth-dark-surface-raised: #39323f;
@auth-dark-border: #453e4f;
@auth-dark-content: #e9e5eb;
@auth-dark-content-muted: #b5b0bd;
@auth-dark-link: #a396e8;
@auth-dark-danger-bg: #3b2733;
@auth-dark-danger-border: #6b3a44;
@auth-dark-danger-content: #f3b0b5;

@media (prefers-color-scheme: dark) {
  body.auth {
    background: @auth-dark-bg;
    color: @auth-dark-content;

    a {
      color: @auth-dark-link;
    }

    // The tiled pattern is light line art, so once the backdrop behind it is
    // dark it reads as a subtle highlight rather than a wash of gray.
    .pattern-bg {
      background-color: @auth-dark-bg;
      opacity: 0.1;
    }

    .box {
      background: @auth-dark-surface;
      border-color: @auth-dark-border;
      box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.4);
    }

    .box .box-header {
      background: @auth-dark-surface-raised;
      color: @auth-dark-content;
      border-bottom-color: @auth-dark-border;
    }

    .auth-container.border-bottom {
      border-bottom-color: @auth-dark-border;
    }

    .auth-provider-column {
      border-left-color: @auth-dark-border;
    }

    .auth-container .help-center-link {
      color: @auth-dark-link;
    }

    .auth-footer .secondary {
      color: @auth-dark-content-muted;

      &:hover {
        color: @auth-dark-content;
      }
    }

    .nav-tabs > li > a {
      color: @auth-dark-content-muted;

      &:hover,
      &:active,
      &:focus {
        color: @auth-dark-content;
      }
    }

    .nav-tabs > li.active {
      a,
      a:hover,
      a:focus {
        color: @auth-dark-content;
      }
    }

    .form-control {
      background: @auth-dark-bg;
      border-color: @auth-dark-border;
      color: @auth-dark-content;
      box-shadow: inset 0 2px 0 rgba(0, 0, 0, 0.12);

      &::placeholder {
        color: @auth-dark-content-muted;
      }

      &:focus {
        border-color: @purple-light;
        box-shadow:
          inset 0 2px 0 rgba(0, 0, 0, 0.12),
          0 0 6px rgba(108, 95, 199, 0.5);
      }

      // Chrome paints autofilled inputs with an opaque light background that
      // ignores `background-color`; an inset shadow is the only way to cover it.
      &:-webkit-autofill,
      &:-webkit-autofill:hover,
      &:-webkit-autofill:focus {
        -webkit-text-fill-color: @auth-dark-content;
        box-shadow: inset 0 0 0 1000px @auth-dark-bg;
        caret-color: @auth-dark-content;
      }
    }

    .help-block {
      color: @auth-dark-content-muted;
    }

    .btn-default {
      color: @auth-dark-content;
      background: @auth-dark-surface-raised;
      border-color: @auth-dark-border;

      &:hover {
        color: @auth-dark-content;
        background: lighten(@auth-dark-surface-raised, 4);
        border-color: lighten(@auth-dark-border, 6);
      }

      &:hover:active,
      &:focus,
      &:active,
      &.active,
      &.active:hover {
        color: @auth-dark-content;
        background: darken(@auth-dark-surface-raised, 3);
        border-color: lighten(@auth-dark-border, 6);
      }
    }

    // Both marks are solid black and would disappear against a dark button.
    // Every other provider logo is full color and needs no adjustment.
    .provider-logo.github,
    .provider-logo.rippling {
      filter: invert(1);
    }

    .alert-danger {
      background: @auth-dark-danger-bg;
      border-color: @auth-dark-danger-border;
      color: @auth-dark-danger-content;
    }

    .error,
    .has-error .help-block,
    .has-error .control-label {
      color: @auth-dark-danger-content;
    }

    .has-error .form-control {
      border-color: @auth-dark-danger-border;

      &:focus {
        border-color: @auth-dark-danger-border;
      }
    }
  }
}

Start with static/less/auth.less, which styles the Django-rendered authentication screens, and compare the existing light-mode selectors with the dark-mode behavior shown in the issue. Implement the prefers-color-scheme rules there, then run the relevant frontend or asset-build checks and verify the authentication screens in a dark browser setting.