sub_kw = dict(facecolor='azure')
fig_kw = dict(facecolor='silver')
fig, ((ax1, ax2), (ax3, ax4)) = plt.subplots(2, 2, subplot_kw=sub_kw, **fig_kw)
ax1.plot(x, y)
ax2.scatter(x, y)
ax4.set_facecolor('pink')