controller:

    $crud->add_action('this should be on the right side', '',
    'admin/reject_all_applicant_status', 'fa fa-times-circle
    red_force');

    $crud->add_action('button 2', '',
    'admin/process_applicant_status', 'fa fa-clipboard
    green_color');

    $crud->add_action('button 3', '',
    'admin/reject_applicant_status', 'fa fa-times red_color');

    css:
    .red_color{
    color:red !important;
    }

    .red_force{
    margin-left:auto;
    float:right !important;
    color:red !important;
    }

    .green_color{
    color:green !important;
    }