highchart background with three colorfull

Question

I can create just one part of this Chart background! i need your help ....

       var chartOptions = {
        type: 'scatter',
        backgroundColor: {
            linearGradient: {
                x1: 0,
                y1: 0,
                x2: 1,
                y2: 0.7
            },
            stops: [
                [0, '#8F9DB9'], 
                [0, '#AADBED']
            ]
        },
    }

at the end of my sample is

var xAxis = chart.xAxis[0];
chartOptions.backgroundColor.stops[0][0] = 0.45

what does above line ?