python的matplotlib 3D怎么更换背景颜色？

Question

from mpl_toolkits.mplot3d import Axes3Dimport matplotlib.pyplot as pltimport numpy as npplt.rcParams['font.sans-serif']=['STSong']plt.rcParams['axes.unicode_minus']=Falsefig=plt.figure()ax=fig.add_subplot(111,projection='3d')a=np.arange(0,1,0.1)b=a*2c=2*np.sin(a)ax.scatter(a,b,c,color='green')ax.set_xticks([])ax.set_yticks([])ax.set_zticks([])ax.set_xlabel("甲")ax.set_ylabel("乙")ax.set_zlabel("丙")ax.grid(False)plt.show()如何把银灰色去掉啊？