You can add code on GridView OnRowCreated Event like :
if (e.Row.RowType == DataControlRowType.DataRow)
{
if (e.Row.RowState == DataControlRowState.Alternate)
{
e.Row.Attributes.Add("onmouseover", "this.style.backgroundColor=MouseOvercolor;");
e.Row.Attributes.Add("onmouseout", "this.style.backgroundColor=MouseOutColor;");
}
else
{
e.Row.Attributes.Add("onmouseover", "this.style.backgroundColor=MouseOverColor;");
e.Row.Attributes.Add("onmouseout", "this.style.backgroundColor=MouseOutColor;");
}
}