Graphically denote which phase of graph each plot represents: original or new. I was thinking that if they were firstly shown in the same color, but the new graphs would be thicker (a larger linewidth value).

Be sure to output the new line so that it overlaps the old line (is layered over it)

First plot: unlabeled, smaller linewidth, alpha reduced

Could use dotted lines to represent hypothetical movements

This is a great resource for info about using Matplotlib:

Quiz system (stating, testing hypotheses; checking whether a variable changed after being presented with a graphical change)

"Baseline plot" might be hardcoded or set in relative terms, relative to the previous run of the code — the latter could get confusing.