I'm assuming that the repo/collection that hosts the to-be-reviewed versions of the PsfSn_goodCModel_stars_scatter and PsfSn_goodCModel_all_scatter is /repo/main and collection u/sr525/plotTests.  If there are other plots I should look at, let me know.

Reviewed on GH, just one additional soft suggestion that I mention on GH also but repeat here: I think it might be instructive to run an example of this kind of plot for something other than a mag as the x axis. To me, this would help make clear whether a distinction really is necessary between `xCol` and `magCol`, and also whether there are any other built-in gotchas that come from all of the usage to date being with mag as x-col. In other words, this is built as a general x-y scatter plot thing, but as is it might work actually less generally than intended (especially with the drawing of the paths, etc.), in which case maybe we should be content with this being just more narrowly a MagScatterHistPlot or something.

All looks good!