<ul>
  <li>repeat</li>
  <li>repeat-x</li>
  <li>repeat-y</li>
  <li>no-repeat</li>
  <li>round</li>
  <li>space</li>
  <li>round space</li>
  <li>space round</li>
</ul>
body {
  width: 100vw;
  height: 100vh;
  background: #293e78 url("https://source.unsplash.com/W_9mOGUwR08/200x200") repeat left top;
  background-blend-mode:screen, luminosity; 
}

ul {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate3d(-50%,-50%,0);
  white-space: nowrap;
  color: #fff;
  margin: 0;
  padding: 0;
  list-style: none outside none;
  
  li {
    display: inline-block;
    padding: 5px 20px;
    background: #29B4F0;
    font-size: 1.5em;
    cursor: pointer;
    border-radius: 3px;
    margin: 5px;
    box-shadow: 0 0 3px rgba(#000, .3);
    background-blend-mode: screen ,difference;
  }
}
View Compiled
(function(){
  var contanier = document.body;
  var repeat = ["repeat", "repeat-x","repeat-y","no-repeat","round", "space", "round space","space round"];
  var btns = document.querySelectorAll('li');
  [].forEach.call(btns,function(btn,index){
    btn.addEventListener('click',function(){
      document.body.style.backgroundRepeat = repeat[index];
    });
  })
})();

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External JavaScript

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