Is there a style key for Josm's default style

I’m editing here:

and I’m guessing that the different colours actually mean something. Is there a map key somewhere?

(pressing “help” reveals only “The page En_GB:Help does not exist. You can create it here.” - but I suspect that’s because I haven’t upgraded Josm in a while)

Edit: There is this - but it’s not a map key, and I’m not going to read all that text.

There’s only the stylesheet itself elemstyles.mapcss in josm/trunk/resources/styles/standard – JOSM
Most styles don’t have visualization in the documentation. Only some exceptions. Styles/Coloured_buildings – JOSM
Not even the old ver has it Styles/LegacyStandard – JOSM

Unfortunately I think the best way to learn the representation of map features in the josm default style is to simply select them in the editor and check their tags. There is no map key that I’m aware of.