Factorplot calls the default base pointplot function, which takes the markers argument. This is used to differentiate markers. The size for all lines and markers can be changed using the scale argument.
exercise = sns.load_dataset("exercise") g = sns.factorplot(x="time", y="pulse", hue="kind", data=exercise, ci=95, markers=['o', 'v', 's'], scale = 1.5)
Same data as above, with different shapes
Also pay attention to the ci argument in your example. 95 will cause ci to be unlikely to see another shape.
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