paperless-ngx/src-ui/src/theme_dark.scss

$bg-dark-mode: #161618;
$bg-light-dark-mode: #1c1c1f;
$text-color-dark-mode: #abb2bf;
$text-color-dark-mode-accent: lighten($text-color-dark-mode, 10%);
$border-color-dark-mode: #47494f;

* {
  transition: background-color 0.3s ease, border-color 0.3s ease;
}
@mixin dark-mode {
  background-color: $bg-dark-mode !important;
  color: $text-color-dark-mode;

  .navbar-brand {
    color: $text-color-dark-mode;
  }

  .bg-light {
    background-color: $bg-light-dark-mode !important;

    a,
    div {
      color: $text-color-dark-mode !important;
    }
  }

  .border,
  .border-bottom,
  .border-left,
  .border-right {
    border-color: $border-color-dark-mode !important;
  }

  .nav-link.active {
    background-color: $bg-dark-mode;
    color: $text-color-dark-mode;
    border-color: $border-color-dark-mode $border-color-dark-mode $bg-dark-mode;
  }

  .nav-link:hover {
    border-color: $border-color-dark-mode $border-color-dark-mode $bg-dark-mode;
  }

  .nav-tabs {
    border-color: $border-color-dark-mode;
  }

  .dropdown-menu {
    background-color: $bg-dark-mode;

    .dropdown-divider {
      border-color: $border-color-dark-mode;
    }

    .dropdown-item {
      color: $text-color-dark-mode;

      &:hover {
        background-color: $bg-light-dark-mode;
        color: $text-color-dark-mode;
      }
    }

    .dropdown-item.disabled {
      color: darken($text-color-dark-mode, 20%);
    }
  }

  .card {
    background-color: $bg-light-dark-mode;

    .card-text {
      color: $text-color-dark-mode;
    }
  }

  app-tag .badge {
    opacity: 0.8;
    color: $bg-dark-mode !important;
  }

  .badge-light {
    background-color: darken($bg-dark-mode, 20%);
    color: $text-color-dark-mode-accent;
  }

  .doc-img {
    background-color: lighten($bg-light-dark-mode, 30%);
    mix-blend-mode: soft-light;
  }

  .doc-img-background {
    background-color: lighten($bg-light-dark-mode, 30%);
  }

  .doc-img-background-selected {
    background-color: lighten($bg-light-dark-mode, 35%);
  }

  .toast {
    background-color: opacify($bg-light-dark-mode, .85);
  }

  .toast-header {
    background-color: opacify($bg-dark-mode, .85);
  }

  a:hover {
    color: lighten($primary, 10%);
  }

  table {
    background-color: $bg-dark-mode;
    color: $text-color-dark-mode;
    border-color: $border-color-dark-mode;
  }

  .table td,
  .table th {
    border-color: $border-color-dark-mode;
  }

  .table-row-selected {
    background-color: $bg-light-dark-mode;
  }

  .close {
    text-shadow: 0 1px 0 #666;
  }

  .btn-outline-primary:hover {
    background-color: darken($primary, 10%);
    color: $text-color-dark-mode-accent;
  }

  .btn-outline-secondary {
    border-color: $border-color-dark-mode;
    color: $border-color-dark-mode;

    &:hover {
      background-color: $bg-dark-mode;
    }
  }

  .btn-link:hover,
  .btn-outline-primary:not(:disabled):not(.disabled).active,
  .btn-outline-primary:not(:disabled):not(.disabled):active,
  .show > .btn-outline-primary.dropdown-toggle {
    color: $text-color-dark-mode-accent;
  }

  .form-control,
  input,
  select,
  textarea {
    background-color: $bg-dark-mode;
    color: $text-color-dark-mode;
    border-color: $border-color-dark-mode;

    &::placeholder {
      color: $text-color-dark-mode;
    }

    &:focus {
      background-color: $bg-light-dark-mode !important;
      color: darken($text-color-dark-mode, 10%) !important;
    }
  }

  .ng-select-container,
  .ng-select.ng-select-opened > .ng-select-container,
  .ng-dropdown-panel,
  .ng-dropdown-panel .ng-dropdown-panel-items .ng-option {
    background-color: $bg-dark-mode;
    color: $text-color-dark-mode;
    border-color: $border-color-dark-mode;

    input:focus {
      background-color: $bg-dark-mode !important;
    }
  }

  .ng-dropdown-panel .ng-dropdown-panel-items .ng-option:hover {
    background-color: $bg-light-dark-mode;
  }

  .custom-control-label:before {
    background-color: $bg-dark-mode;
    color: $text-color-dark-mode;
  }

  .custom-control-input:checked ~ .custom-control-label::before {
    color: $text-color-dark-mode-accent;
  }

  .input-group-text {
    color: $text-color-dark-mode;
    background-color: $bg-light-dark-mode;
    border-color: $border-color-dark-mode;
  }

  .list-group-item {
    color: $text-color-dark-mode;
    background-color: $bg-light-dark-mode;
    border-color: $border-color-dark-mode;
  }

  .page-item.disabled .page-link {
    background-color: $bg-dark-mode;
    border-color: $border-color-dark-mode;
  }

  .list-group-item,
  .page-link {
    background-color: $bg-light-dark-mode;
    border-color: $border-color-dark-mode;
  }

  .page-item.active .page-link {
    border-color: $border-color-dark-mode;
    color: $text-color-dark-mode-accent;
  }
}

body.dark-mode {
  @include dark-mode;
}
@media (prefers-color-scheme: dark) {
  body.dark-mode-preferred {
    @include dark-mode;
  }
}