Interesting that so much of the country seems dissatisfied with their current time zone. Being in WA, I'm certainly hoping that it moves forward for us.
The linked page portrays it as e.g. CA moving to "MST" but that doesn't actually accurately represent what's proposed, because the lack of a DST switch is meaningfully different from just moving to the same timezone as current Mountain time states.
The page is trying to provide a visual for how "off" our maps and tzdata are going to be if laws like these pass without a unified vision of the move. What sort of reasonable thing is California and western Kansas being in the same time zone but not Utah?
EDIT: And after all that, there will still be states that will observe daylight savings time.
Though I do agree that the graphic could be better, as the important information is really just: will the winter time move/not move 1 hour, and will the state observe/not observe daylight savings time. They need to add crosshatching or similar to indicate the latter info.
Current federal law does not allow you to stay on "Daylight" time year round while you can stay on "Standard" year round.
Essentially, gray means "would stay on daylight savings time," i.e., follow the time to their left in winter and to their right in summer. The colors mean "would stay on this time year-round." So if a state changes color, it means "drop DST and use summer time", and if it stays the same, it means "drop DST and use winter time."
The states that would stay on winter time are ID, AZ, CO, NM, ND, KS, OK, HI, AK, IL, MI, OH, NY, PA. The states that would stay on summer time are WA, OR, CA, MT, WY, UT, MN, IA, MO, AR, TN, MS, AL, FL, SC, NC, WV, DE, CT, RI, VT, NH, MA, ME, DC. Some are undecided as what to do (i.e., GA, TX and VA), while IN proposes to move to the Central Time winter time rather than stay in either Eastern summer or winter time.
So, yes it is confusing, and a bit incomplete - thanks for your efforts to decode it!