>2.0.1 Update As commented by @CatherineHolloway you need to use facecolor instead of color now:
import matplotlib.pyplot as plt
plt.plot([0,1],[0,1],ls="--",c="b")
plt.fill_between([0,1],[0,1], facecolor="none", hatch="X", edgecolor="b", linewidth=0.0)
plt.show()
Former answer
This seems to do the trick!
import matplotlib.pyplot as plt
plt.plot([0,1],[0,1],ls="--",c="b")
plt.fill_between([0,1],[0,1], color="none", hatch="X", edgecolor="b", linewidth=0.0)
plt.show()
