It depends where you want to apply your custom css class.

CSS class for table row

If you want to add the custom class to the <tr> element, I recommend to overwrite the function single_row like so:

public function single_row( $item ) {
    $cssClass = ($item['view_status '] == 1) ? 'make-it-green' : 'make-it-grey';
    echo '<tr class="'.$cssClass.'">';
    $this->single_row_columns( $item );
    echo '</tr>';
}

CSS class for table cell

Use the column_{column name} functions like you have outlined it with column_default and put a HTML tag as a wrapper within the cell. For example a span element:

public function column_default( $item, $column_name ) {
    $cssClass = ($item['view_status '] == 1) ? 'make-it-green' : 'make-it-grey';
    switch ( $column_name ) {           
        case 'id':
            return '<span class="'.$cssClass.'">'.$item[$column_name].'</span>';
        default:
          return $item[$column_name];
    }
}