Here's the rules if you want to add more here (developed by
@nirvn and myself)

- Keep colors in the "middle" - avoid too light or too dark colors,
too light colors will make line layers invisible on the
default white background, too dark colors are too visually heavy
for polygon areas

- Avoid over saturated/pure colors, which are too visually heavy. E.g.

- No blues! Blues have a single meaning on maps (water) and we're
almost never going to fluke that a randomly assigned blue color
is given to a water feature layer. So we just avoid blues altogether
as users are almost always going to have to change layers away
from blue anyway.

- Avoid yellow. Yellow is used as the default selected feature color
in QGIS, so keep colors well away from this yellow to avoid confusion
between selected/unselected yellow layers

- Keep things "happy", "positive" and "friendly". No baby puke green/browns