how to add overlay color in css code example

Example 1: How to overlay image with color in CSS?

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

Example 2: overlay color on image css

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);
}