>>> import numpy as np
>>> import matplotlib.patches
>>> rect = matplotlib.patches.Rectangle([0, 0], 1, 1)
>>> rect.set_hatchcolor(np.zeros(3))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/larsoner/python/matplotlib/lib/matplotlib/patches.py", line 445, in set_hatchcolor
    self._set_hatchcolor(color)
  File "/home/larsoner/python/matplotlib/lib/matplotlib/patches.py", line 428, in _set_hatchcolor
    if color == 'edge':
       ^^^^^^^^^^^^^^^
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()