zen-desktop/src/browser/base/content/zen-styles/zen-theme.css

/* Here, we contain all the theme related variables, for example theme
 * colors, border radius, etc.
 * We have `--zen-border-radius` and `--zen-primary-color` as variables.
 */

:host(:is(.anonymous-content-host, notification-message)),
:root,
.zenLooksAndFeelColorOption {
  /** We also add `.zenLooksAndFeelColorOption` so that it recalculates the colors when the theme changes
  * in the preferences page.
  */

  /* Default values */
  --zen-border-radius: 7px;
  --zen-primary-color: #4a90e2;

  /** Zen colors are generated automatically from the primary color */
  --zen-colors-primary: color-mix(in srgb, var(--zen-primary-color) 50%, black 50%);
  --zen-colors-secondary: color-mix(in srgb, var(--zen-colors-primary) 20%, white 80%);
  --zen-colors-tertiary: color-mix(in srgb, var(--zen-primary-color) 2%, white 98%);

  --zen-colors-hover-bg: color-mix(in srgb, var(--zen-primary-color) 90%, white 10%);
  --zen-colors-primary-foreground: color-mix(in srgb, var(--zen-primary-color) 80%, black 20%);
  --zen-colors-border: color-mix(in srgb, var(--zen-colors-secondary) 98%, black 2%);

  --zen-colors-input-bg: color-mix(in srgb, var(--zen-primary-color) 1%, var(--zen-colors-tertiary) 99%);

  --zen-dialog-background: var(--zen-colors-tertiary);
  --zen-urlbar-background: color-mix(in srgb, var(--zen-primary-color) 3%, #f4f4f4 97%);

  --zen-secondary-btn-color: var(--zen-colors-primary-foreground);

  --in-content-primary-button-background: light-dark(
    color-mix(in srgb, var(--zen-primary-color) 35%, black 65%),
    color-mix(in srgb, var(--zen-primary-color) 35%, white 65%)
  ) !important;
  --in-content-primary-button-background-hover: light-dark(
    color-mix(in srgb, var(--zen-primary-color) 40%, black 60%),
    color-mix(in srgb, var(--zen-primary-color) 40%, white 60%)
  ) !important;
  --in-content-primary-button-background-active: var(--zen-colors-hover-bg) !important;
  --in-content-primary-button-text-color: light-dark(white, black) !important;
  --in-content-primary-button-border-color: transparent !important;
  --in-content-primary-button-border-hover: transparent !important;
  --in-content-primary-button-border-active: var(--zen-colors-border) !important;
  --in-content-box-border-color: var(--zen-colors-border) !important;

  --in-content-accent-color: var(--zen-colors-primary) !important;

  /* This is like the secondary button */
  --in-content-button-background: light-dark(
    color-mix(in srgb, var(--zen-primary-color) 20%, transparent 80%),
    color-mix(in srgb, var(--zen-primary-color) 10%, transparent 90%)
  ) !important;
  --in-content-button-background-hover: light-dark(
    color-mix(in srgb, var(--zen-primary-color) 5%, rgba(0, 0, 0, 0.1) 95%),
    color-mix(in srgb, var(--zen-primary-color) 15%, transparent 85%)
  ) !important;
  --button-bgcolor: var(--in-content-button-background) !important;
  --button-hover-bgcolor: var(--in-content-button-background-hover) !important;
  --focus-outline-color: var(--button-bgcolor) !important;
  --in-content-button-text-color: var(--zen-secondary-btn-color) !important;

  --toolbarbutton-icon-fill-attention: var(--zen-primary-color) !important;

  --button-primary-bgcolor: var(--in-content-primary-button-background) !important;
  --button-primary-hover-bgcolor: var(--in-content-primary-button-background-hover) !important;
  --button-primary-active-bgcolor: var(--in-content-primary-button-background-active) !important;
  --button-primary-color: var(--in-content-primary-button-text-color) !important;

  --color-accent-primary-hover: var(--zen-primary-color) !important;

  --in-content-page-background: var(--zen-colors-tertiary) !important;
  --zen-in-content-dialog-background: var(--zen-colors-tertiary);

  --zen-button-border-radius: 7px;
  --zen-button-padding: 0.6rem 1.2rem;

  /* Toolbar */
  --zen-toolbar-height: 39px;
  --zen-toolbar-button-inner-padding: 6px;
  --toolbarbutton-outer-padding: 4px;

  /* Other colors */
  --urlbar-box-bgcolor: var(--zen-urlbar-background) !important;
  --urlbar-box-active-bgcolor: var(--toolbarbutton-hover-background) !important;
  --toolbar-field-focus-background-color: var(--urlbar-box-bgcolor) !important;
  --zen-input-border-color: light-dark(rgb(204, 204, 204), rgb(66, 65, 77));

  /* XUL */
  --zen-main-browser-background: light-dark(rgb(235, 235, 235), #1b1b1b);
  --zen-browser-gradient-base: color-mix(in srgb, var(--zen-primary-color) 50%, white 50%);

  --zen-appcontent-border: 1px solid var(--zen-colors-border);
  --zen-panel-radius: var(--zen-border-radius);

  --toolbarbutton-border-radius: 6px;

  --fp-contextmenu-border-radius: 8px;
  --fp-contextmenu-padding: calc(4px - var(--fp-contextmenu-menuitem-border-width)) 0;
  --fp-contextmenu-menuitem-border-radius: calc(4px + var(--fp-contextmenu-menuitem-border-width));
  --fp-contextmenu-menuitem-padding-block: 6px;
  --fp-contextmenu-menuitem-padding-inline: 10px;
  --fp-contextmenu-menuitem-border-width: 2px;
  --fp-contextmenu-menuicon-margin-inline: 12px;
  --fp-contextmenu-menuitem-margin-inline: calc(4px - var(--fp-contextmenu-menuitem-border-width));
  --fp-contextmenu-menuitem-margin-block: 0px;
  --fp-contextmenu-menuitem-margin: var(--fp-contextmenu-menuitem-margin-block) var(--fp-contextmenu-menuitem-margin-inline);
  --fp-contextmenu-separator-vertical: calc(4px - var(--fp-contextmenu-menuitem-border-width));
  --fp-contextmenu-separator-horizontal: 0;
  --fp-contextmenu-bgcolor: light-dark(Menu, rgb(43 42 51 / 0.95));
  --toolbar-bgcolor: transparent;

  --toolbarbutton-active-background: var(--zen-colors-border) !important;

  --input-bgcolor: var(--zen-colors-tertiary) !important;
  --input-border-color: var(--zen-input-border-color) !important;
  --zen-themed-toolbar-bg: light-dark(#fdfdfd, var(--zen-colors-tertiary)) !important;

  --toolbar-field-background-color: var(--zen-colors-input-bg) !important;
  --arrowpanel-background: var(--zen-dialog-background) !important;
}

@media (prefers-color-scheme: dark) {
  :host(:is(.anonymous-content-host, notification-message)),
  :root {
    --zen-in-content-dialog-background: rgb(23, 23, 23);
    --zen-dark-color-mix-base: rgb(21, 21, 21);
    --zen-colors-primary: color-mix(in srgb, var(--zen-primary-color) 20%, var(--zen-dark-color-mix-base) 80%);
    --zen-colors-secondary: color-mix(in srgb, var(--zen-primary-color) 30%, var(--zen-dark-color-mix-base) 70%);
    --zen-colors-tertiary: color-mix(in srgb, var(--zen-primary-color) 1%, var(--zen-dark-color-mix-base) 99%);

    --zen-colors-hover-bg: color-mix(in srgb, var(--zen-primary-color) 90%, var(--zen-dark-color-mix-base) 10%);
    --zen-colors-primary-foreground: color-mix(in srgb, var(--zen-primary-color) 80%, white 20%);

    --zen-colors-input-bg: color-mix(in srgb, var(--zen-primary-color) 1%, var(--zen-dark-color-mix-base) 99%);
    --zen-colors-border: color-mix(in srgb, var(--zen-colors-secondary) 20%, rgb(43, 43, 43) 80%);

    --zen-dialog-background: var(--zen-dark-color-mix-base);
    --zen-urlbar-background: color-mix(in srgb, var(--zen-primary-color) 4%, rgb(24, 24, 24) 96%);

    --zen-browser-gradient-base: color-mix(in srgb, var(--zen-primary-color) 30%, var(--zen-dark-color-mix-base) 70%);
  }
}

@media (prefers-color-scheme: dark) {
  @media (-moz-bool-pref: 'zen.theme.color-prefs.amoled') {
    :root {
      --zen-dark-color-mix-base: hsl(5 5 5);
      --zen-urlbar-background: color-mix(in srgb, var(--zen-primary-color) 4%, rgb(0, 0, 0) 96%);
    }
  }

  @media (-moz-bool-pref: 'zen.theme.color-prefs.colorful') {
    :root {
      --zen-in-content-dialog-background: rgb(28, 28, 32);

      --zen-colors-primary: color-mix(in srgb, var(--zen-primary-color) 50%, black 50%);
      --zen-colors-secondary: color-mix(in srgb, var(--zen-primary-color) 40%, black 60%);
      --zen-colors-tertiary: color-mix(in srgb, var(--zen-primary-color) 15%, black 85%);

      --zen-colors-hover-bg: color-mix(in srgb, var(--zen-primary-color) 90%, black 10%);
      --zen-colors-primary-foreground: color-mix(in srgb, var(--zen-primary-color) 80%, white 20%);

      --zen-colors-input-bg: color-mix(in srgb, var(--zen-primary-color) 10%, black 80%);
      --zen-colors-border: color-mix(in srgb, var(--zen-colors-secondary) 80%, black 20%);

      --zen-dialog-background: color-mix(in srgb, var(--zen-primary-color) 10%, black 90%);
      --zen-urlbar-background: color-mix(in srgb, var(--zen-primary-color) 8%, rgb(15, 15, 15) 92%);

      --zen-browser-gradient-base: color-mix(in srgb, var(--zen-primary-color) 30%, black 70%);
    }
  }
}

@media not (-moz-bool-pref: 'zen.theme.toolbar-themed') {
  :root {
    --toolbar-bgcolor: light-dark(#e6e6e6, #1b1b1b) !important;
    --zen-themed-toolbar-bg: var(--toolbar-bgcolor);
  }
}