Untitled

<style>
tr td {vertical-align:top}

td{width:100px;height:100px;background-color: green}

table#aa tr:not(.jack):nth-child(even) td {
    background-color: blue;

}


table#bb tr.reg:nth-child(even) td {
    background-color: blue;

}


</style>
</head>
<body>

<table id="aa">
<tr><td></td><td></td></tr>
<tr class="jack"><td></td><td></td></tr>
<tr><td></td><td></td></tr>
<tr><td></td><td></td></tr>
</table>

<table id="bb">
<tr class="reg"><td></td><td></td></tr>
<tr><td></td><td></td></tr>
<tr class="reg"><td></td><td></td></tr>
<tr class="reg"><td></td><td></td></tr>
</table>


</body>