The chart seem to be async so you will probably need to provide a callback when the animation has finished or else the canvas will be empty.

var options = {
    bezierCurve : false,
    onAnimationComplete: done  /// calls function done() {} at end
};

If you want a customized background color then, you'd have to draw a background with your preferred color, and you can do so, like this ...

var backgroundColor = 'white';
Chart.plugins.register({
    beforeDraw: function(c) {
        var ctx = c.chart.ctx;
        ctx.fillStyle = backgroundColor;
        ctx.fillRect(0, 0, c.chart.width, c.chart.height);
    }
});

DEMO

// draw background
var backgroundColor = 'white';
Chart.plugins.register({
    beforeDraw: function(c) {
        var ctx = c.chart.ctx;
        ctx.fillStyle = backgroundColor;
        ctx.fillRect(0, 0, c.chart.width, c.chart.height);
    }
});

// chart
var canvas = $('#NoBidsChart').get(0);
var myChart = new Chart(canvas, {
    type: 'line',
    data: {
        labels: [1, 2, 3, 4, 5],
        datasets: [{
            label: 'Line Chart',
            data: [1, 2, 3, 4, 5],
            backgroundColor: 'rgba(255, 0, 0, 0.2)',
            borderColor: 'rgba(255, 0, 0, 0.5)',
            pointBackgroundColor: 'black'
        }]
    }
});

// save as image
$('#save').click(function() {
    canvas.toBlob(function(blob) {
        saveAs(blob, "pretty image.png");
    });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/FileSaver.js/1.3.3/FileSaver.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.min.js"></script>
<button id="save">Save</button>
<canvas id="NoBidsChart"></canvas>

Chart.js is built on the HTML5 canvas element.

To use it on node.js you need to mimic this element in node.

There is a package that try to handle all the needed libraries for this purpose, you can find it here chartjs-node