use kartik\export\ExportMenu;
use kartik\grid\GridView;
echo ExportMenu::widget([
    'dataProvider' => $dataProvider,
    'columns' => [
        [
            'class' => 'kartik\grid\SerialColumn', 
            'exportMenuStyle' => [ // format the serial column cells
                'fill' => [
                    'fillType' => \PhpOffice\PhpSpreadsheet\Style\Fill::FILL_SOLID, 
                    'color' => ['argb' => 'FFE5E5E5']
                ]
            ]
        ],
        ['attribute' => 'id', 'hAlign' => GridView::ALIGN_CENTER],
        'name',
        [
            'attribute'=>'author_id',  // note this column config is changed in ExportMenu vs GridView
            'label'=>'Author',
            'value'=>function ($model, $key, $index, $widget) { 
                return $model->author->name;
            }
        ],
        [
            'attribute'=>'color',
            'width'=>'100px',
            'exportMenuStyle' => function($model, $key, $index, $column) { // as a Closure function
                $colors = [
                    'blue' => 'FF0000FF',
                    'black' => 'FF000000',
                    'brown' => 'FFA52A2A',
                    'cyan' => 'FF00FFFF',
                    'red' => 'FFFF0000',
                    'green' => 'FF008000',
                    'orange' => 'FFFFA500',
                    'pink' => 'FFFFC0CB',
                    'yellow' => 'FFFFFF00',
                ];
                return ['font'=>['bold'=>true, 'color'=>['argb' => $colors[$model->color]]]];
            }
        ],
        [
            'attribute'=>'publish_date', 
            'exportMenuStyle' => ['numberFormat' => ['formatCode' => 'YYYY-MM-DD']] // formats a date
        ],
        [
            'attribute'=>'status', // note this column config is changed in ExportMenu vs GridView
        ],
        // next 2 columns will be auto-formatted based on decimal format set
        ['attribute'=>'buy_amount','format'=>['decimal',2], 'hAlign'=>'right', 'width'=>'110px'], 
        ['attribute'=>'sell_amount','format'=>['decimal',2], 'hAlign'=>'right', 'width'=>'110px'],
        // skip rendering the Action Column in export menu
        // ['class' => 'kartik\grid\ActionColumn', 'urlCreator'=>function(){return '#';}]
    ],
    'dropdownOptions' => [
        'label' => 'Export All',
        'class' => 'btn btn-outline-secondary btn-default'
    ]
]) . "<hr>\n".
GridView::widget([
    'dataProvider' => $dataProvider,
    'columns' =>  $gridColumns
]);

$gridColumns = [
    ['class' => 'kartik\grid\SerialColumn'],
    'id',
    'name',
    [
        'attribute'=>'author_id',
        'label'=>'Author',
        'vAlign'=>'middle',
        'width'=>'190px',
        'value'=>function ($model, $key, $index, $widget) { 
            return Html::a($model->author->name, '#', []);
        },
        'format'=>'raw'
    ],
    'color',
    'publish_date',
    'status',
    ['attribute'=>'buy_amount','format'=>['decimal',2], 'hAlign'=>'right', 'width'=>'110px'],
    ['attribute'=>'sell_amount','format'=>['decimal',2], 'hAlign'=>'right', 'width'=>'110px'],
    ['class' => 'kartik\grid\ActionColumn', 'urlCreator'=>function(){return '#';}]
];