The figure background color is not respected by savefig(). MWE:
import matplotlib.pyplot as plt
fig = plt.figure()
plt.plot([1, 2, 3], [1, 2, 3])
plt.gca().set_facecolor('#2d2d2d')
plt.gcf().patch.set_facecolor('#2d2d2d')
# plt.show()
plt.savefig("out.png")
show():

savefig():
