A coloured box?

Thanks. and I also manage to find the video that explain what I intend to do:

    <style>

      .colimg200 {

        height: 200px;

        background: #aaa;

      }

      .colimg100 {

        height: 88px;

        background: #bbb;

      }

    </style>

   <div class="container mt-2">

      <!-- (a) 2 equal width columns -->

      <div class="row">

        <!-- colum 1 -->

        <div class="col-sm-8 bg-dark colimg200"></div>

        <!-- column 2 -->

        <div class="col-sm-4">

          <!-- row 1 -->

          <div class="row colimg100 ml-2 mb-4">

            <div class="col-sm-12"></div>

          </div>

          <!-- row 2 -->

          <div class="row colimg100 ml-2">

            <div class="col-sm-12"></div>

          </div>

        </div>

      </div>

    </div>

Because I do not want to include contents. And the above will produce the desired boxes and lightly coloured.

Thanks for the encouragement.