lineColor: String

Sets the color of the custom break lines. Custom Break line color can be a “HTML Color Name” or “hex” code.

var  chart =  new  CanvasJS.Chart("chartContainer",
{
 .
 .
 axisY: {
	scaleBreaks: {
		customBreaks: [{
			lineColor: "blue",
			.
			.
		}]
	}
 },
 .
 . 
});
chart.render();