I believe that you are using RadChartView not RadGridView. In this case, you can use the following code to remove the BackColor and change the lines style:
CartesianArea area =
CartesianGrid grid = area.GetGrid<CartesianGrid>();
grid.BorderDashStyle = System.Drawing.Drawing2D.DashStyle.Solid;
I hope this will be useful. Let me know if you have additional questions.