The colour can be green, red, yellow, orange and more rarely, brown, white, rainbow (between stages of ripening), lavender and dark purple, depending on the variety of pepper.
Some red peppers are simply ripened green peppers. Green peppers are less sweet and slightly more bitter than yellow or orange peppers, with red bell peppers being the sweetest.
Bell peppers, like most other vegetables, retain highest nutritional value when they are consumed in raw form. And all bell peppers, of all colours, are suitable for raw consumption.