titleBackgroundColor: String

Sets the axisY Title background color. The value of titleBackgroundColor can be “HTML Color Name”, “hex code”, or “rgba values”.

var  chart =  new  CanvasJS.Chart("container",
{
 .
 .
 axisY:{
       title: "Axis Y Title",
       titleBackgroundColor:"#A4CBEF"
 },
 .
 . 
});
chart.render();