I decided to stitch the body of the dolphin and the lighter green of the "green" in the diagonal mosaic. I like the texture it adds. I also did the palm tree trunks in the chain stitch to make them look nice and "barky".
When I first finished stitching, I noticed that the shading on my grapefruits was too dark and noticeable. See this photograph.
So I picked out the dark shading and put in the lighter pink from the dolphin. I think it looks much more natural.