Think of humans... Not everyone is alike, but we are all the same species, Homo sapiens. We all have similar characteristics, like two arms, five fingers per hand, etc., but not all of us are exactly alike.
All Sarr species have their own general physical characteristics. However, most species are divided up into varieties and cultivars because of variability within a given species. Each individual is similar to other individuals within it's own species, but variability should be expected because not all individuals in a given species have the same genetic makeup.
Also note that younger plants tend to look different than fully mature plants. In addition, if you are speaking of hybrids you should know that almost anything goes thanks to the wonderful world of genetics.
Here is where I look to to get good pictures and descriptions of Sarrs:
-http://www.sarracenia.com/faq.html (Scroll down to the Sarracenia section.)
-http://www.cpphotofinder.com/Sarracenia.html