Background color line chart not used

protected function getData(): array
{
    return [
        'datasets' => [
            [
                'label' => 'Offertes',
                'data' => [0, 10, 5, 2, 21, 32, 45, 74, 65, 45, 77, 89],
                'backgroundColor' => '#36A2EB',
                'borderColor' => '#9BD0F5',
                'tension' => 0.4,
            ],
            [
                'label' => 'Orderbevestigingen',
                'data' => [0, 3, 1, 5, 4, 6, 4, 8, 3, 9, 5, 110],
                'backgroundColor' => '#19e123',
                'borderColor' => '#006baf',
                'tension' => 0.4,
            ]
        ],
        'labels' => ['Jan', 'Feb', 'Mrt', 'Apr', 'Mei', 'Jun', 'Jul', 'Aug', 'Sep', 'Okt', 'Nov', 'Dec']
    ];
}