Match Curve Styles 

In[1]:=

X styles = Sequence @@ {ImageSize -> 400, Filling -> Axis, FillingStyle -> Opacity[0.1], PlotRange -> {0.01, All}, AxesOrigin -> {-0.01, 0.01}, PlotStyle -> (Directive[AbsoluteThickness[5], #] & /@ ColorData[68, "ColorList"])};

Curve styles are automatically matched when creating a plot legend.

In[2]:=

X Plot[Table[ Sqrt[Cos[t]] Exp[-x Sin[t]^4], {x, {1, 10, 100, 1000, 10000}}] // Evaluate, {t, 0, Pi/2}, Evaluate@styles, PlotLegends -> LineLegend[{1, 10, 100, 1000, 10000}, LegendMarkerSize -> {30, 10}, LegendLabel -> x, LabelStyle -> {GrayLevel[0.3], Bold, 16}]]

Out[2]=