dynamic bgrnd opacity

setting bgrnd opacity for alternate rows, regardless of bgrnd color

by WOUNDEDStevenJones

HTML

<script src="//code.jquery.com/jquery-3.3.1.slim.min.js"></script>
<link rel="stylesheet" href="//stackpath.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css">
<script src="//cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.0/umd/popper.min.js"></script>
<script src="//stackpath.bootstrapcdn.com/bootstrap/4.1.0/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
<div class="container">
  <div id="table">
    <div class="row a">
      Row 1 / Cat 1
    </div>
    <div class="row a">
      Row 2 / Cat 1
    </div>
    <div class="row a">
      Row 3 / Cat 1
    </div>
    <div class="row b">
      Row 4 / Cat 2
    </div>
    <div class="row b">
      Row 5 / Cat 2
    </div>
    <div class="row c">
      Row 6 / Cat 3
    </div>
    <div class="row c">
      Row 7 / Cat 3
    </div>
    <div class="row c">
      Row 8 / Cat 3
    </div>
  </div>
</div>

CSS

.container {   padding: 20px; }
.row {   padding: 5px 15px;  border-bottom: 1px solid black; }
.a {   background-color: rgb(173, 216, 230, 1); /*lightblue*/ }
.b {   background-color: rgb(255, 165, 0, 1); /*orange*/ }
.c {   background-color: rgb(144, 238, 144, 1); /*lightgreen*/ }
.row:nth-child(1) {   border-top: 1px solid black; }

.row.a:nth-child(even) {
  background-color: rgb(173, 216, 230, .6); /*lightblue opaque*/
}
.row.b:nth-child(even) {
  background-color: rgb(255, 165, 0, .6); /*orange opaque*/
}
.row.c:nth-child(even) {
  background-color: rgb(144, 238, 144, .6); /*lightgreen opaque*/
}