mdb-ui-kit/scss/_tables.scss

// BS4 has not yet converted the following to variables - keep an eye on it and move to variables when possible.
.thead-inverse {
  th {
    //color: $bmd-inverse; // #fff;
    //background-color: $gray-dark;
  }
}
.thead-default {
  th {
    //color: $gray;
    //background-color: $bmd-inverse-lighter; //$gray-lighter;
  }
}

.table-inverse {
  color: $bmd-inverse-light; //$gray-lighter;
  //background-color: $gray-dark;

  //th,
  //td,
  //thead th {
  //  border-color: $gray;
  //}
}