Have to write code in your c# file because in crystal report there is not an option for setting formula to change line style and color
if (...)
{
LineObject lo = (LineObject)Report.ReportDefinition.ReportObjects["Line1"];
lo.LineStyle = CrystalDecisions.Shared.LineStyle.DashLine;
lo.LineColor = Color.DarkRed;
}
Happy Coding!
:)