framework/less/lib/mixins/light-contents.less

// This is a mixin which styles components (buttons, inputs, etc.) for use on
// dark backgrounds.
.light-contents(@color: #fff, @control-bg: fade(#000, 10%), @control-color: #fff) {
  &, a {
    color: @color;
  }
  .Button--link, .Search-input {
    color: @control-color;
  }
  .FormControl {
    background: @control-bg;
    border: 0;
    color: @control-color;
    .placeholder(@control-color);

    &:focus {
      color: @color;
      background: fadein(darken(@control-bg, 5%), 10%);
    }
  }
  .Button, .Button:hover {
    color: @control-color;
    background: @control-bg;
  }
  .Button--flat {
    background: transparent;
  }
  .Button:active,
  .Button.active,
  .Button:focus,
  .Button.focus,
  .open > .Dropdown-toggle.Button {
    background: fadein(@control-bg, 5%);
    color: @control-color;
  }
}