How might the snow-white berries be a kind of foreshadowing that adds tension to the story?

The classical novel "Romeo and Juliet" by William Shakespeare, uses foreshadowing as a tool to let readers know that the protagonists are destined to fall in love just to die later. It is a classic example of a story of love, dramatic irony, suspense and tension for the audience. The use of snow-white berries during the novel foreshadows the inevitable die that Romeo and Juliet face since snow-white berries are the counterpart of cadava berries, pink berries that are poisonous and whose name is a pun for cadaver.