Untitled

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
/* Popup container - can be anything you want */
.popup {
  position: relative;
  display: inline-block;
  cursor: pointer;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}

/* The actual popup */
.popup .popuptext {
  visibility: hidden;
  width: 160px;
  background-color: #555;
  color: #fff;
  text-align: center;
  border-radius: 6px;
  padding: 8px 0;
  position: absolute;
  z-index: 1;
  bottom: 125%;
  left: 50%;
  margin-left: -80px;
}

/* Popup arrow */
.popup .popuptext::after {
  content: "";
  position: absolute;
  top: 100%;
  left: 50%;
  margin-left: -5px;
  border-width: 5px;
  border-style: solid;
  border-color: #555 transparent transparent transparent;
}

/* Toggle this class - hide and show the popup */
.popup .show {
  visibility: visible;
  -webkit-animation: fadeIn 1s;
  animation: fadeIn 1s;
}

/* Add animation (fade in the popup) */
@-webkit-keyframes fadeIn {
  from {opacity: 0;}
  to {opacity: 1;}
}

@keyframes fadeIn {
  from {opacity: 0;}
  to {opacity:1 ;}
}
</style>
</head>
<script type="text/javascript">
function CheckColors(val){
 var element=document.getElementById('color');
 if(val=='others'){
 document.getElementById("test").style.display= "block";
 } else {
document.getElementById("test").style.display= "none";
 }
}

</script>
</head>
<body>
  <select id="color" onchange='CheckColors(this.value);'>
    <option>pick a color</option>
    <option value="red">RED</option>
    <option value="blue">BLUE</option>
    <option value="others">others</option>
  </select>

  <div class="form-group" id="test" style = display:none >
    <label>Size</label>
    <select class="form-control" id="size">
    		   <option value = "null">Choose a size...</option>
               <option value = "6">6</option>
               <option value = "6.5">6.5</option>
               <option value = "7">7</option>
 			   <option value = "7.5">7.5</option>
               <option value = "8">8</option>
               <option value = "8.5">8.5</option>
    		   <option value = "9">9</option>
               <option value = "9.5">9.5</option>
               <option value = "10">10</option>
               <option value = "10.5">10.5</option>
 			   <option value = "11">11</option>
               <option value = "11.5">11.5</option>
               <option value = "12">12</option>
               <option value = "12.5">12.5</option>
               <option value = "13">13</option>
    </select>
  </div>

</body>
</html>