Colloid-gtk-theme/src/sass/gnome-shell/widgets-47-0/_switches.scss

/* Switches */

$switch_width: 46px;
$switch_handle_size: 20px;

.toggle-switch {
  width: $switch_width;
  border-radius: $circular-radius;
  transition-duration: 100ms;
  color: $text;
  background: transparentize(if($variant == 'light', black, white), .85);

  &:hover {
    background: transparentize(if($variant == 'light', black, white), .8);
  }

  StIcon {
    icon-size: $base_icon_size;
  }

  .handle {
    margin: 3px;
    width: $switch_handle_size;
    height: $switch_handle_size;
    border-radius: $circular-radius;
    background: if($variant == 'light', white, mix(white, $background, 80%));
    box-shadow: 0 2px 4px transparentize(black, .8);
    transition-duration: 100ms;
  }

  &:checked {
    background: $primary;
    color: $primary-text;

    &:hover {
      @if $gnome_version == 'default' {
        background-color: lighten($primary, 5%);
        color: lighten($primary-text, 5%);
      } @else {
        background-color: st-lighten($primary, 5%);
        color: st-lighten($primary-text, 5%);
      }
    }

    .handle {
      background: white;
    }
  }
}