A chart point that presents an item.
Value type: Object 
 borderColor - (string) the outer color of an item marker
 
 borderWidth - (integer) the width of the border line (by default, 2)
 
 color - (string) the inner color of an item marker
 
 radius - (integer) the item radius (by default, 4)
 
 type - ('round' or 'r', 'square' or 's', 'diamond' or 'd') the shape of items markers (by default, 'round')
 
var chart =  new dhtmlXChart({
	...
        item:{
               borderColor:"#ffffff",
               color:"#000000"
        },
        ...
})
or
chart.define("item",{
			borderColor:"#ffffff",
                        color:"#000000"
		},
);