Okay...what's the narrative significance regarding the skin colour of dwarves?
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First of all "Sam" is not digusted by green eggs and ham... "Sam-I-Am" is the one trying to get the unnamed subject to try Green Eggs and ham.
Also, if you want to dig that deep into it...than not even the type of food matters in the story. The important thing is that the subject has already decided that he does not like X...even though he has never actually tried X. X could be anything. Sam-I-Am could be presenting Red peas and lamb and we'd arrive at the same point...without even changing the rhyming scheme. Sam-I-Am is not telling the subject that he should try rotten food. The moral of the story is that you should try new foods before writing them off. It's really not that complex.