If you paint a canvas hive with a color, then leave the world or server (works both in single and multiplayer) the color gets reset. tested in version productivebees-1.21.0-13.3.2 in the atm10 modpack.

I can't recreate this, it keeps the color just fine when I relog

Seems to have been fixed with the same update that fixed the canvas hives not connecting to any pipez or other options.