Change placeholder color of a input field

// style.scss 
$input-color: rgba(0, 0, 0, 0.7);

input {
    &::placeholder {
      color: $input-color;
      opacity: 0.6;
    }
    &::-webkit-input-placeholder {
      /* WebKit browsers */
      color: $input-color;
      opacity: 0.6;
    }
    &:-moz-placeholder {
      /* Mozilla Firefox 4 to 18 */
      color: $input-color;
      opacity: 0.6;
    }
    &::-moz-placeholder {
      /* Mozilla Firefox 19+ */
      color: $input-color;
      opacity: 0.6;
    }
    &:-ms-input-placeholder {
      /* Internet Explorer 10+ */
      color: $input-color;
      opacity: 0.6;
    }
  }