There are other bright red mushrooms (especially russulas) which are quite tasty. Russulas also can have many other bright colors. Conversely, many of the deadliest mushrooms where I live are plain and unassuming, at least in the color spectrum I can see.

Not exactly. You can eat that mushroom but you'll have indigestion problems. Squirrels around me love it though. You can also parboil it and you'll be fine, which it is actually quite tasty.

That mushroom (Amanita muscaria) is also related to the death cap (Amanita phalloides). Though the toxins are different in the death cap and will not be converted/removed by parboiling. Worse than that, you won't show symptoms for over a day.

The death cap is white or yellow, looking quite mundane. Especially compared to Muscaria.