I finally got around to fixing the colors of the LED animations on the display device. For a long time, I thought that something had changed subtly in the color model used by ESPHome and that it would be a lot of bother for me to get back to the colors I wanted (and that show in the videos on this project). It turned out to be something simpler, though still an infrastructure change somewhere along the way.
To give the totally awesome "world on fire" look to the display, I'm using the ESPHome fastled component. Specifically, I'm using the addressable flicker effect. It has a tunable parameter for how much the flickering can vary from the base color of the LED. I had been using 25%, which looked good in the original incarnation with an older ESPHome release. I cranked that "intensity" value way down and, after some experimentation, settled on 7% variation. It now looks pretty much like I wanted.
I have updated waterwatcher55.yaml to reflect this change (and to correct one other unrelated typo.)
This is probably the last log entry for this project. That is, unless I think of something else. :-)