<style>
  body {
        background-color: white;
        color: black;
      }

      body.dark {
        background-color: black;
        color: white;
      }

      body.red {
        background-color: #ff8080;
        color: white;
      }

      body.blue {
        background-color: #80b3ff;
        color: white;
      }

      body.green {
        background-color: #80ff80;
        color: black;
      }

      body.orange {
        background-color: #ffbf80;
        color: black;
      }

      body.purple {
        background-color: #bf80ff;
        color: white;
      }

      .theme-container {
        margin-top: 20px;
      }

      #change-theme-btn {
        background-color: #4CAF50;
        color: white;
        padding: 10px 20px;
        border: none;
        cursor: pointer;
        border-radius: 10px;
      }

      #change-theme-btn:hover {
        background-color: #3e8e41;
      }

      label {
        margin-right: 10px;
        font-weight: bold;
      }

      select {
        padding: 5px;
      }
    </style>