> And the poisonous ones apparently don't use color as a warning signal, and don't smell all that bad, and some of the poisons have really mild effects, like "gives only some people diarrhea" or "makes a hangover worse".

Some of the poisonous ones even taste really good, and don't start making you sick for a day or two (and then you die horribly). You hear about it from time to time, where people have the best dinner of their life and then are dead.

You're likely referring to the death cap (Amanita phalloides), which is reportedly quite tasty. But there's also a mushroom that's both deadly poisonous and a sought-after, commercially sold delicacy, the only difference being the method of preparation:

https://en.wikipedia.org/wiki/Gyromitra_esculenta

Although recent research suggests that some poison remains even after careful preparation, and that consumption may even be linked to ALS (Lou Gehrig's disease).