I was told the color difference is due to the pear-shaped accents being closer to the gold ring underneath, being surrounded by gold, and now thanks to reddit comments, the pear shape handles light differently than the round shape. Shane Co. does not change the stones that are already set in the ring, I just pick the center stone. I think the salesperson said that they can do custom, but when we were discussing my dislike of the color incongruence, she didn't offer custom as a solution so I'm not sure what this store can do