So the sorcerer's elemental bloodline has a special rider which states that the spells granted by your bloodline have the damage type of your specific element (fire for the fire element, bludgeoning for everything else). The cantrip you are automatically given is "produce flame." If I have an earth-element for my bloodline, but want to have a cantrip that does fire damage, is there anything stopping me from learning "produce flame" a second time? For slotted spells, I can always learn them at a higher level, but I don't know about cantrips.
Don't have any solid answer, but as GM I would allow learn the cantrip a second time with the "correct" elemento.
I'd likely allow that as well.
I do wonder if Pathfinder Society will allow it, though.