change svg color in pseudo element

p:after {
  width: 48px;
  height: 48px;
  display: inline-block;
  content: '';
  -webkit-mask: url(https://gist.githubusercontent.com/mmathys/fbbfbc171233a30e478ad5b87ec4f5d8/raw/cd9219e336b8f3b85579015bdce9665def091bb8/heart.svg) no-repeat 50% 50%;
  mask: url(https://gist.githubusercontent.com/mmathys/fbbfbc171233a30e478ad5b87ec4f5d8/raw/cd9219e336b8f3b85579015bdce9665def091bb8/heart.svg) no-repeat 50% 50%;
  -webkit-mask-size: cover;
  mask-size: cover;
}

.red:after {
  background-color: red;
}

.green:after {
  background-color: green;
}

.blue:after {
  background-color: blue;
}