MVC3中使用的jqGrid的背景颜色怎么修改

UsersGrid = new JQGrid
{
Columns = new List()
{
new JQGridColumn { DataField = "UserID",
// always set PrimaryKey for Add,Edit,Delete operations
// if not set, the first column will be assumed as primary key
PrimaryKey = true,
Editable = false,
HeaderText="序号",
Width = 50,
CssClass="_color"
},
new JQGridColumn { DataField = "UserName",
Editable = true,
Width = 100,
DataFormatString = "{0:d}" ,
HeaderText="用户名"},
new JQGridColumn { DataField = "Password",
Editable = true,
Width = 100 ,
HeaderText="口令"},
new JQGridColumn { DataField = "Description",
Editable = true,
Width = 75 ,
HeaderText="描述"}
},
//设置背景颜色
Width = Unit.Pixel(640) ,
Height = Unit.Pixel(500)
};

UsersGrid.ToolBarSettings.ShowRefreshButton = true;