Is the Guy-Who-Is-Not-Sam-I-Am reluctant to eat the titular dish based on its appearance/color alone, or is his refusal based on his self-proclaimed dislike of Sam-I-Am and the subsequent desire to not give Sam the satisfaction of having got him to do something?
Is Sam-I-Am just someone who wants to share food? Or is he a stalker who won't relent until he gets his way? Is he persistent? Or is he an example of how not to market products?
Family-Unfriendly Aesop: Sam-I-Am is basically harassing the grumpy character, refusing to take a clear "no" for an answer. Regardless of his (presumably) good intentions that is really not behavior that should be demonstrated to children. Really, is it unfair of the guy to be wary of green eggs and ham?
Fan Nickname: Sam-I'm-Not for the nameless character Sam-I-Am keeps pestering.
Ho Yay: It's possible to see the book as having a gay subtext. Sam-I-Am is offering something at once familiar and yet with an initially-unappealing aspect to it to Sam-I'm-Not ... like same-sex relations. He is convinced that Sam-I'm-Not really, really, deep down inside likes it and he knows this. Sam-I'm-Not resists this doggedly, which has to make Sam-I-Am even more convinced that he understands Sam-I'm-Not better than he himself does.
The Living Books adaptation becomes especially suspect to this by the end, with Sam-I'm-Not preparing and feeding Sam-I-Am a giant (blue) roast turkey and eventually leading up to them both walking arm-in-arm into the sunset.