body {
  background-color: #008080;
  background-image: 
    linear-gradient(45deg,#000000 0%, #000000 25%, transparent 25%, transparent 75%, #000000 75%, #000000 100%),
    linear-gradient(45deg,#000000 0%, #000000 25%, transparent 25%, transparent 75%, #000000 75%, #000000 100%);
  background-position: 0 0, 25px 25px;
  background-repeat: repeat;
  background-size: 50px 50px;
}