JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdn.jsdelivr.net/npm/bootstrap@4.4.1/dist/js/bootstrap.bundle.min.js"></script>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@4.4.1/dist/css/bootstrap.min.css">
<div class="container">
  <div class="table-responsive">
    <table class="table table-bordered text-center">
      <thead>
        <tr class="bg-light-gray">
          <th class="text-uppercase"></th>
          <th class="text-uppercase">Uhrzeit</th>
          <th class="day-1 text-uppercase">Montag</th>
          <th class="day-2 text-uppercase">Dienstag</th>
          <th class="day-3 text-uppercase">Mittwoch</th>
          <th class="day-4 text-uppercase">Donnerstag</th>
          <th class="day-5 text-uppercase">Freitag</th>
        </tr>
      </thead>
      <tbody>
        <tr>
          <td class="align-middle">1. Stunde</td>
          <td class="align-middle">08:00</td>
          <td class="day-1">
            <span class="bg-yellow padding-5px-tb padding-15px-lr border-radius-5 margin-10px-bottom text-white font-size16 xs-font-size13">GU</span>
          </td>
          <td class="day-2">
            <span class="bg-yellow padding-5px-tb padding-15px-lr border-radius-5 margin-10px-bottom text-white font-size16  xs-font-size13">GU</span>
          </td>

          <td class="day-3">
            <span class="bg-yellow padding-5px-tb padding-15px-lr border-radius-5 margin-10px-bottom text-white font-size16  xs-font-size13">GU</span>
          </td>
          <td class="day-4">
            <span class="bg-yellow padding-5px-tb padding-15px-lr border-radius-5 margin-10px-bottom text-white font-size16  xs-font-size13">GU</span>
          </td>
          <td class="day-5">
            <span class="bg-yellow padding-5px-tb padding-15px-lr border-radius-5 margin-10px-bottom text-white font-size16  xs-font-size13">GU</span>
          </td>
        </tr>
        
        <tr>
          <td class="bg-light-gray"></td>
          <td class="bg-light-gray">08:50</td>
...

CSS

body{
    margin-top:20px;
}
.bg-light-gray {
    background-color: #f7f7f7;
}
.table-bordered thead td, .table-bordered thead th {
    border-bottom-width: 2px;
}
.table thead th {
    vertical-align: bottom;
    border-bottom: 2px solid #dee2e6;
}
.table-bordered td, .table-bordered th {
    border: 1px solid #dee2e6;
}


.bg-sky.box-shadow {
    box-shadow: 0px 5px 0px 0px #00a2a7
}

.bg-orange.box-shadow {
    box-shadow: 0px 5px 0px 0px #af4305
}

.bg-green.box-shadow {
    box-shadow: 0px 5px 0px 0px #4ca520
}

.bg-yellow.box-shadow {
    box-shadow: 0px 5px 0px 0px #dcbf02
}

.bg-pink.box-shadow {
    box-shadow: 0px 5px 0px 0px #e82d8b
}

.bg-purple.box-shadow {
    box-shadow: 0px 5px 0px 0px #8343e8
}

.bg-lightred.box-shadow {
    box-shadow: 0px 5px 0px 0px #d84213
}


.bg-sky {
    background-color: #02c2c7
}

.bg-orange {
    background-color: #e95601
}

.bg-green {
    background-color: #5bbd2a
}

.bg-yellow {
    background-color: #f0d001
}

.bg-pink {
    background-color: #ff48a4
}

.bg-purple {
    background-color: #9d60ff
}

.bg-lightred {
    background-color: #ff5722
}

.padding-15px-lr {
    padding-left: 15px;
    padding-right: 15px;
}
.padding-5px-tb {
    padding-top: 5px;
    padding-bottom: 5px;
}
.margin-10px-bottom {
    margin-bottom: 10px;
}
.border-radius-5 {
    border-radius: 5px;
}

.margin-10px-top {
    margin-top: 10px;
}
.font-size14 {
    font-size: 14px;
}

.text-light-gray {
    color: #d6d5d5;
}
.font-size13 {
    font-size: 13px;
}

.table-bordered td, .table-bordered th {
    border: 1px solid #dee2e6;
}
.table td, .table th {
    padding: .75rem;
    vertical-align: top;
    border-top: 1px solid #dee2e6;
}

.opening-day { 
  background-color: yellow; 
}