Updated code to use matplotlib.colormaps["Blues"] as matplotlib.cm.get_cmap() is deprecated (see https://matplotlib.org/stable/api/prev_api_changes/api_changes_3.7.0.html#deprecation-of-top-level-cmap-registration-and-access-functions-in-mpl-cm )

Description

Motivation and Context

Resolves: #474

How Has This Been Tested?

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• I have updated the documentation (if relevant).
• I have added tests that cover my changes (if relevant).
• The modified code is cuda compatible (github tests don't test cuda) (if relevant).
• I have updated the CHANGELOG.