How do I change the marker edge color of a seaborn relplot?
The issue was with the parameter I was using. The parameter "edgecolors" is incorrect. The correct parameter is the non-plural "edgecolor". So the correct call to relplot is:

sns.relplot(data=df, x="values_x", y="values_y", edgecolor=None)


This would remove the marker edges completely, which is what I was trying to do originally.