When Undine responds to Mrs. Fairford's invitation, she puts a lot of thought into which paper she will use to write back. The narrator, in Chapter 2, describes her choice with careful imagery:
She had read in the 'Boudoir Chat' of one of the Sunday papers that the smartest women were using the new pigeon-blood note-paper with white ink; and rather against her mother's advice she had ordered a large supply, with her monogram in silver. It was a disappointment, therefore, to find that Mrs. Fairford wrote on the old-fashioned white sheet, without even a monogram––simply her address and telephone number. It gave undine a rather poor opinion of Mrs. Fairford's social standing, and for a moment she thought with considerable satisfaction of answering the note on her pigeon-blood paper.
Compared to Mrs. Fairford's white paper, this red "pigeon-blood" paper helps depict Undine's ambitious character. Undine is very excited to use her distinctive paper, always wanting to find a way to be, at once, different from those around her but also following a trend. Undine loves novelty, but she also impulsively imitates anyone she admires; her red paper, inspired by "Boudoir Chat," is a prime example of this. The contrasting red and white leaves of paper figuratively show Undine's stylish need for individuality. On the other side, Undine also finds in this interaction that the Fairfords will not be the useful entrée into polite society she had hoped. This disappointment, too, is depicted visually in the color of the paper.
Pigeon-blood paper was a fad in the early 20th century; it was bright red and more common in stamps than in letter paper. Pigeons were then widely believed to have especially beautiful ruby-red blood. At the end of the novel, Elmer's wedding gifts to Undine are "a necklace and tiara of pigeon-blood rubies belonging to Queen Marie Antoinette, a million dollar cheque and a house in New York." Pigeon-blood, matching her "reddish-gold hair," must be a favorite of Undine's, perhaps since she learned about it in "Boudoir Chat." This color, and how Undine came to be attached to it, are fruitful images that describe her character.
In Chapter 2, the narrator creates a vivid picture when Undine prepares in her room at the Stentorian for her dinner party at the Fairford residence. As she chooses from her dresses, the narrative uses visual imagery to describe how Undine shines in the room's electric light:
Céleste, before leaving, had drawn down the blinds and turned on the electric light, and the white and gold room, with its blazing wall-brackets, formed a sufficiently brilliant background to carry out the illusion. So untempered a glare would have been destructive to all half-tones and subtleties of modelling; but Undine's beauty was as vivid, and almost as crude, as the brightness suffusing it. Her black brows, her reddish-tawny hair and the pure red and white of her complexion defied the searching decomposing radiance: she might have been some fabled creature whose home was in a beam of light.
Undine, just before this passage, sat herself in front of the mirror with a fan and gloves to emulate a high-society woman. (This is the "illusion" referred to in the passage above.) Drenched in harsh light, this image of Undine is a figurative description of her character. Her appearance is especially suited for electric light, because her beauty is "as vivid, and almost as crude, as the brightness suffusing it." This reflects on her character: just as her beauty has no "half-tones or subtleties," Undine's perspective on the world lacks nuance, as she becomes entirely caught up in her desires.
Electric light was still new at the time of the novel. But Undine already seems to belong in it, like "some fabled creature whose home was in a beam of light." This also illuminates Undine's character. She clamors for instant fame and gratification, reflected in the instant convenience of a light switch.
In Chapter 21, Ralph stays in New York with his son Paul while Undine neglects her family in Europe with Peter. Ralph tries in vain to navigate the relationship between himself, his son, and his parents-in-law, while his wife is gone in Paris. Ralph and the Spraggs, in regular visits at their new apartment in the Malibran, usually awkwardly talk about Undine. But when Undine stops sending Ralph letters, conversation becomes even more awkward. Ralph tries to improve things by enlisting the Spraggs as babysitters:
To escape the strain of these visits, Ralph once or twice tried the experiment of leaving Paul with his grand-parents and calling him for the late afternoon; but one day, on entering the Malibran, he was met by a small abashed figure clad in a kaleidoscopic tartan and a green velvet cap with a silver thistle. After this experience of the "surprises" of which Gran'ma was capable when she had the chance to take Paul shopping Ralph did not again venture to leave his son, and their subsequent Saturdays were passed together in the sultry gloom of the Malibran.
Paul's clothes, as is so often the case with Undine, are used here as imagery to represent the state of his family. Ralph and the Spraggs do not get along because they have nothing in common. Paul is caught in the middle, as his grandparents still want to see him, and it becomes awkward for all involved. Paul's clashing, badly styled clothes represent the tension in the family. This association is especially strong because Paul does not choose his clothes, as "Gran'ma" seemingly dressed him up against his will. Paul, as only a young child, bears the burden of the discord between Ralph and the Spraggs, without any other choice; in much the same way, he didn't choose the clashing clothes on his body.