JSFiddle - React, Tailwind, and code Playground

HTML

<table width="284" border="1">
 
    <tr class="entete">
    <td>Jours</td>
    <td width="15">A</td>
    <td width="15">B</td>
    <td width="15">C</td>
    <td width="15">D</td>
    <td width="15">E</td>
    </tr>
    </table>
    <br/>
 
    <table border="1">
 
    <tr class="semaine">
    <td width="70">Vendredi</td>
    <td width="10">1</td>
    <td width="70">Février</td>
    <td width="15">M</td>
    <td width="15">R</td>
    <td width="15">R</td>
    <td width="15">N</td>
    <td width="15">A</td>
    </tr>
 
    <tr class="semaine">
    <td>Samedi</td>
    <td>2</td>
    <td>Février</td>
    <td>R</td>
    <td>R</td>
    <td>M</td>
    <td>N</td>
    <td>A</td>
    </tr>
 
    <tr class="weekend">
    <td>dimanche</td>
    <td>3</td>
    <td>Février</td>
    <td>R</td>
    <td>R</td>
    <td>M</td>
    <td>N</td>
    <td>A</td>
    </tr>
 
    <tr class="weekend">
    <td>Lundi</td>
    <td>4</td>
    <td>Février</td>
    <td>N</td>
    <td>A</td>
    <td>M</td>
    <td>R</td>
    <td>R</td>
    </tr>
 
    <tr class="semaine">
    <td>Mardi</td>
    <td>5</td>
    <td>Février</td>
    <td>N</td>
    <td>A</td>
    <td>M</td>
    <td>R</td>
    <td>R</td>
    </tr>
 
	<tr class="semaine">
    <td>Mercredi</td>
    <td>6</td>
    <td>Février</td>
    <td>N</td>
    <td>A</td>
    <td>R</td>
    <td>R</td>
    <td>M</td>
    </tr>
 
    <tr class="semaine">
    <td>Jeudi</td>
    <td>7</td>
    <td>Février</td>
    <td>R</td>
    <td>R</td>
    <td>N</td>
    <td>A</td>
    <td>M</td>
    </tr>
 
    <tr class="semaine">
    <td>Vendredi</td>
    <td>8</td>
    <td>Février</td>
    <td>R</td>
    <td>R</td>
    <td>N</td>
    <td>A</td>
    <td>M</td>
    </tr>
 
    <tr class="weekend">
    <td>Samedi</td>
    <td>9</td>
    <td>Février</td>
    <td>R</td>
    <td>M</td>
    <td>N</td>
    <td>A</td>
    <td>R</td>
    </tr>
 
    <tr class="weekend">
    <td>Dimanche</td>
    <td>10</td>
    <td>Février</td>
    <td>R</td>
    <td>M</td>
    <td>N</td>
...

CSS

.repos {background-color:pink;}
.matin {background-color:gold;}
.apresmidi {background-color:lime;}
.nuit {background-color:navy;
color :white;}

JavaScript

$("tr:gt(0) > td").addClass( function(){
    ret="";
 switch ( $(this).text()){
    case"R" : ret='repos';
              break;
    case"M" : ret='matin';
              break;
case"A" : ret='apresmidi';
              break;
case"N" : ret='nuit';
              break;
              }
               return ret; })