A useful overlay Userstyle for adding to your localhost (sometimes the live admin and local are easy to mix up). On the live admin I uncomment the animation and make it fluoro green.

localhost.css

.page-template-default,
body #wrapper {
    position: relative;
}

body #wrapper:before,
body #wrapper:after {
    display: block;
    position: fixed;
    content: '';
    width: 99%;
    height: 97vh;
    outline: 3px dodgerblue dashed;
    top: 0.5vh;
    left: 0.5%;
    pointer-events: none;
    z-index: 99
}
.page-template-default:before,
body #wrapper:before{
    display: block;
    position: fixed;
    content: '👵 localhost 👵';
    color: #eee;
    border: 3px #eee  dashed;
    font-size: 18px;
    text-align: center;
    padding:0.3rem;
    height:auto;
    outline: none;
    width: 10rem;
    background: dodgerblue  ;
    top: 0px;
    right: 4%;
    left:auto;
    pointer-events:none;
    z-index: 9999;
    /*animation: blinker 2s infinite ease-in-out;*/
    box-shadow: 0px 3px 9px #000;
}
@keyframes blinker {
  50% {
    color: yellow;
  }
}