import matplotlib.pyplot as plt
C1 = [(4,1), (2,3), (3,5), (5,4), (1,6), (-1,6)]
C2 = [(0,2), (-2,2), (-3,2), (-2,4)]
C3 = [(1,-2), (3,-2)]
plt.scatter([i[0] for i in C1],[i[1] for i in C1], c='b')
plt.scatter([i[0] for i in C2],[i[1] for i in C2], c='r')
plt.scatter([i[0] for i in C3],[i[1] for i in C3], c='g')
plt.show()