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",
{
 .
 .
 axisX: {
     scaleBreaks: {
	 customBreaks: [{
	      lineColor: "blue",
              .
              .
	}]
     }
 },
 .
 . 
});
chart.render();