overlay color on image css

  background: linear-gradient(#3204fdba, #9907facc), url(https://picsum.photos/1280/853/?random=1) no-repeat top center;

#hero{
  background-image:url();
  background-size:cover;
  background-position:top center;
  position:relative;
}

#hero::after{
  content:'';
  position:absolute;
  left:0;
  top:0;
  height:100%;
  width:100%;
  background-color:black;
  opacity:0.7;
}

html, body{
  min-height: 100%;
}
body{
  position: relative;
}
.overlay{
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 10;
  background-color: rgba(0,0,0,0.5); /*dim the background*/
}

html, body {
  min-height: 100%;
}

body {
  position: relative; /* needed if you position the pseudo-element absolutely */
}

body:after {
  content: "";
  display: block;
  position: fixed; /* could also be absolute */ 
  top: 0;
  left: 0;
  height: 100%;
  width: 100%;
  z-index: 10;
  background-color: rgba(0,0,0,0.2);
}

footer#site-footer{  
  position:relative;
}

footer#site-footer:before {     /* use before property (pseudo-element)  */
    position: absolute;
    content: '';
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.3);
}