How to make holes in div element

Question

#behind{
    width:100px;
    height:100px;
    background:blue;
}
#container{
    width:100px;
    height:100px;
    background:red;
}
#container div{
    width:20px;
    height:20px;
    margin:2px;
}

<div id="behind">
   <div id="container">
       <div></div>
       <div></div>
       <div></div>
       <div></div>
   </div>
</div>

I want the divs inside the container to be like holes and shows what behind it which is the bleu element with id="behinde" and the rest of space stay red. Notice that I don't want to use svg it should be HTML elements like div