css backgorund colors code example

Example 1: css transparent background color

div {
 opacity:25% ; 
}

Example 2: tint image with background color css

.tinted-image {
  background-image: 
    /* top, transparent red */
    linear-gradient(
      rgba(255, 0, 0, 0.45), 
      rgba(255, 0, 0, 0.45)
    ),
    /* your image */
    url(image.jpg);
}