Python matplotlib decrease size of colorbar labels
If you are here because you're trying to increase font size, but some numbers disappear because of big size with the above answer, you can do
cbar = plt.colorbar()
for t in cbar.ax.get_yticklabels():
t.set_fontsize(20)
Aha! Found the answer here:
cbar.ax.tick_params(labelsize=10)
P.S. Upvote that answer and give Paul some love!