Thanks for the comments @sbowler and @frizzo. Thanks for posting your hardware and versions @frizzo and @NottingHill. So far, after two responses, I'm the only one on an RPi3. Anyone else have this working on an RPi3? I know it seems illogical that the RPi hardware version matter, but from a software view, I haven't found anything missing in my setup.
I have made numerous updates to my installer scripts (https://github.com/andylytical/brewpi-scripts), of most significance is a 'diff' check of all files expected to be copied and a json parser to show that the tilt data is getting collected and logged properly. Both of these checks pass.
But I still have the exact same graph as before, where beer_panel shows all possible tilt colors, redTemp is graphed in green, and redSG is graphed in red. While it is certainly possible I have made a mistake somewhere, I have yet to find it (or them). Maybe I'm looking in the wrong place. Any other thoughts? Really, anything! Maybe it's something so stupid I've overlooked it or made an invalid assumption (aside from, is the power turned on, I've got that one covered).
Or maybe I'll try out @NottingHill's strategy of taking a few days off.