Green bells are not unrippened red bells but their own type of pepper.
I have five types, (green, red, yellow, orange and blush) growing in my garden.
Not sure how this thread morphed from Brussel Sprouts to peppers.
Note that the hot varieties of peppers grow in the hottest countries where they are often used in cooking to disguise the smell and taste of spoiled foods like meats.
How would peppers know to grow and evolve in hot tropical countries to help the inhabitants? Another great mystery of life.