Module 'matplotlib' has no attribute 'colors'
The notebook needs to be restarted for the new installations to take effect.
I am running an Anaconda installation of Python3 64bit on Windows. I have no idea how to put those words in a proper sentence, but I hope it gives enough information. I am taking an Udacity course which wants me to run %matplotlib inline. This gives the following error:   

AttributeError: module 'matplotlib' has no attribute 'colors'   

I get the same error when I run from matplotlib import pylab, but i get no error from import matplotlib.  
I installed matplotlib as follows: conda install -n tensorflow -c conda-forge matplotlib.    
How do I solve this error?  
Kind regards
Per request:
conda list gives  

matplotlib                2.1.0                    py36_1    conda-forge  

and a list of other modules.