How to customize xtragrid column line

using System.Drawing;
using DevExpress.XtraGrid;
using DevExpress.XtraGrid.Views.Grid;
using DevExpress.XtraGrid.Views.Grid.ViewInfo;
using DevExpress.XtraGrid.Drawing;

namespace IndexArb.Common
{
    public class GridCustomHelper
    {
        private DevExpress.XtraGrid.GridControl grid;
        private string[] fieldList;
        public float lineWidth = 2;
        public Color lineColor = Color.DeepSkyBlue;

        public GridCustomHelper(DevExpress.XtraGrid.GridControl grid, params string[] lineNameList)
        {
            this.grid = grid;
            this.fieldList = lineNameList;
            grid.Paint += new System.Windows.Forms.PaintEventHandler(Grid_Paint);
        }

        private void Grid_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
        {
            if (fieldList == null || fieldList.Length == 0)
                return;

            GridControl grid = (GridControl)sender;
            GridView view = (GridView)grid.MainView;
            GridViewInfo viewInfo = view.GetViewInfo() as GridViewInfo;

            foreach (string name in fieldList)
            {
                GridColumnInfoArgs columnInfo = viewInfo.ColumnsInfo[view.Columns[name]];
                if (columnInfo == null)
                    return;
                Point p1, p2;
                p1 = new Point(columnInfo.Bounds.Right, columnInfo.Bounds.Bottom);
                p2 = new Point(columnInfo.Bounds.Right, columnInfo.Bounds.Bottom + viewInfo.ViewRects.RowsTotalHeight);
                e.Graphics.DrawLine(new Pen(lineColor, lineWidth), p1, p2);
            }
        }
    }
}