On the basis of the scatterplot example of matplotlib, how can I change the gray background color of the 3 axes grid planes? I would like to set it to white, keeping the grid lines with the default gray color. I found this question but I couldn't apply it to the example. Thanks.

Using the same example. You can set the pane color using the set_pane_color method as described here http://matplotlib.org/mpl_toolkits/mplot3d/api.html#axis3d. You can set the color using the RGBA tuple:

# scatter3d_demo.py
# ...
# Set the background color of the pane YZ
ax.w_xaxis.set_pane_color((1.0, 1.0, 1.0, 1.0))
plt.show()