var kk2 = document.querySelector("#testc"); 

var options = {
 iterations: Infinity, iterationStart: 0, 
 delay: 0, 
 endDelay: 0, 
 direction: 'alternate', 
 duration: 2000, 
 fill: 'forwards', 
 easing: 'ease-in-out', }
 
  var keyframes = [ 
 {   backgroundColor:"orange"}, 
  {  backgroundColor:"yellow" }
   
  
  ] 
  
  kk2.animate(keyframes, options);