discourse/app/assets/stylesheets/common/input_tip.scss

.popup-tip {
  position: absolute;
  display: block;
  padding: 5px 10px;
  z-index: z("tooltip");
  &.bad {
    background: var(--danger-medium);
    color: white;
    box-shadow: shadow("dropdown");
  }
  &.hide,
  &.good {
    display: none;
  }
  .close {
    float: right;
    color: var(--primary);
    opacity: 0.5;
    font-size: $font-0;
    margin: 0 0 0 4px;
    cursor: pointer;
  }
  .close:hover {
    opacity: 1;
  }
}