How plot GridSearch results?
What I would suggest is to have put the results as a Data frame with
pd.DataFrame(cv.cv_results_)

And then you have the data in a dataframe which is easier to handle.
For the other question (in your comments), once you have the data in a nice dataframe is just about data visualization. How can you put it in a nice visualization?
The easier are either 2d plots or 3d or even contour plots. By googling them and python you will get nice tutorials on how to do it