NicholsPlot[(4 (s+0.5))/(s^2 (s^2+2 s+4)),Frame->True,PlotStyle->Directive[AbsoluteThickness[4],ColorData[24,9]],NicholsGridLines->{{#,Directive[Dashed,Darker@ColorData[24,2]]}&/@{1.01,1.05,1.1,1.25,1.5,1.75,2.25,3,4},{#,Directive[Dotted,Darker@ColorData[24,6]]}&/@({1/2,1,2,5,10,15,25,50,75,-1/2,-1,-2,-5,-10,-15,-25,-50,-75,} Degree)}]