heya healthcare
so as the others have noted, yeah, it's pretty much impossible to say exactly what's in those crosses... for certain, that is. The art of speculation, however, should not be discounted. Although no substitute for a written pedigree, speculation is a skill that can help if you rationally think you can figure out parentages. Sometimes at the nursery I work at, I've been able to deduce a simple, 2 species cross from looking at the characteristics visible (given that the cross was known to include only 2 species, and that it could be backed up with the nursery owner's memory). But again, one's guess is only as good as one's informed experience and rationale. Other factors to take into account besides pitcher shape or color is growth habit, including if the plant produces seasonal traps or phyllodia, and flower color, scent, morphology, and the time of season when it flowers. Responsiveness to seasonal cues is another hint to ancestry. Even the texture of the pitcher's tissue can offer clues to parentage.
Another trick to really discovering pedigree is to do multiple self-pollinations and see what genetic diversity is unlocked in the offspring. When Adrian Slack is selfed, because it's a S. x moorei, plants resembling flava, leucophylla, and intermediaries are present in the progeny. Another fun case of this was when Jerry Addington selfed a supposed S. rosea and got a plant out of the progeny with a white, frilly lid like S. leucophylla. Whether or not the pollination was botched isn't necessary to illustrate that Sarrs contain incredibly diverse genetics, even in specimens assumed to be pure species.