[Chartjs]-Remove background color in chartjs line chart

Set fill property as false in Dataset options

 datasets: [
    {
        label: "",
        fill: false,
        .....
        .......
        data: [65, 59, 80, 0, 56, 55, 40],
    }
]

You can refer this fiddle:
https://jsfiddle.net/red_stapler/u5aanta8/1/

Also Reffer chartJs Docs
https://www.chartjs.org/docs/latest/charts/line.html