When looking for examples of figurative language in 'The Island The Blue Dolphins' look for places where the writing appeals to the reder's senses, whether that is in a good way, or a 'bad' way.' For example, the title itself is a glorious image. Who wouldn't love to be on an island gazing at the peaceful and innocent scene of blue dolphins playing? What a calming and joyful experience that might be. Yet there are dangers lurking underneath most things. The colour blue is emotive, it is gentle and peaceful when thinking in terms of the sea and the sky. But underneath, things are not so nice! Think of sharp coral, spiny poisonous stonefish, sting jellyfish and carniverous creatures.
You could look at the colour red, which is highly emotive in another way, a scary way. It often signifies danger, or things which are forbidden and sometimes makes us think of fights or death because of its association with bloodthirsty battles and violence. We know it is an emotive colour to animals too, think of the term 'like a red rag to a bull' and the rage of the bull against the goading matador. Colour is important in the animal kngdom, significant in areas of territory defence (robins) feeding young (seagull beaks) and insect pollination (bees.) You could also look at the kinds of creatures in the book and write about they might signify in terms of the themes the writer is trying to present or message to be conveyed.