No problem. While fuzzy graphing has existed for a long time as contour plots, I'd still like to encourage you to experiment more. The colors look pretty. :)

I have a suggestion. Calculate z=left-right without absolute value, and try mapping [negative limit, 0, positive limit] to [black, red, white], or possibly [negative limit, 0, positive limit, outside of limits] to [red, white, blue, black]. And of course, do variations and have fun!

I'm not sure I've tried that - might good idea. I've actually been playing with all kind so of visualizations - I've done most of my art as stand-alone Python scripts. Here's an open-source starting point for doing this kind of math art in Python: https://github.com/calebmadrigal/truthygraph.py. You might want to try your idea yourself :)