Exact work:

• implement __copy__ and maybe __deepcopy__ on ColorMap

Tagging as medium because the color map code is a bit convoluted .

I can reproduce this issue with:

import matplotlib.pyplot as plt
import copy
import numpy as np

%matplotlib inline
data = np.ma.masked_array([[1,2,3],[2,3,4]], mask=[[1,0,0],[0,0,0]])
cm = plt.cm.Reds
plt.imshow(data,cmap=cm)
plt.show()
cm2 = copy.copy(cm)
cm2.set_bad('b')
plt.imshow(data,cmap=cm)

In the second plot the image contains blue when it should remain white. copy.deepcopy works as expected, though. Would the solution be to have copy call deepcopy?

Implementing __copy__ should be enough to get the desired behavior.