JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <tr>
        <th>Colonne 1</th>
        <th>Colonne 1</th>
        <th>Colonne 1</th>
    </tr>
    <tr>
        <td colspan=3>cellule 100%</td>
    </tr>
    <tr>
        <td>celulle 33%</td>
        <td>celulle 33%</td>
        <td>celulle 33%</td>
    </tr>            
</table>

CSS

table {
    border-collapse: collapse;
}

td, th {
    border: 1px solid black;
}

tr:nth-child(2){    
    background: green;
}

tr:nth-child(3) td:nth-child(3){
    background: yellow;
}