import numpy as np
import matplotlib.pyplot as plt

import control as ct

# bit of a hack
def findlines(artist):
    return (isinstance(artist, plt.Line2D)
            and artist.get_linestyle()=='-'
            and isinstance(artist.get_xdata(), np.ndarray))

g = ct.tf([1],[1,1]) * ct.tf([1,3],[1,2]) * ct.tf([1],[1,1,16])

ct.rlocus(g);

h = plt.gca().findobj(match=findlines)

for i, h_ in enumerate(h): h_.set_color(f'C{i}')

plt.show()