The rainbow acts as one of many motifs or repeating images that are used throughout the novel to comment upon the various characters and their sexual fulfilment. Let us remember that it appears symbolically early on in the novel as Tom and Lydia walk through a rainbow, signifying their movement towards a more stable relationship, as "she was the doorway to him, he to her." Again, the rainbow is used to symbolise a kind of doorway when Anna's door is said to open directly "under the arch of the rainbow." The rainbow again is used to indicate the way that Anna is moving towards a deep sense of inner satisfaction and fulfilment in her role as a mother.
The final appearance of this important motif appears at the very end of the novel whilst Ursula is shown to be recuperating after her miscarriage. The rainbow again points towards a hopeful and more liberated future for her, as she will be liberated from the restricting roles of wife and mother and can therefore seek her fulfilment where she wills. The motif of the rainbow therefore symbolises the various stages that characters arrive at in their lives and all point towards fulfilment and completeness in their futures.