JSFiddle - React, Tailwind, and code Playground
by glebcha
HTML
<table>
<tr><td>aaaaaaaa</td></tr>
<tr><td>aaaaaaaa</td></tr>
<tr><td>bbbbbbbb</td></tr>
<tr><td>bbbbbbbb</td></tr>
<tr><td>aaaaaaaa</td></tr>
<tr><td>aaaaaaaa</td></tr>
<tr><td>bbbbbbbb</td></tr>
<tr><td>bbbbbbbb</td></tr>
<tr><td>aaaaaaaa</td></tr>
<tr><td>aaaaaaaa</td></tr>
<tr><td>bbbbbbbb</td></tr>
<tr><td>bbbbbbbb</td></tr>
</table>
CSS
table tr:nth-child(4n-1), table tr:nth-child(4n) {
background: #ccc;
}