In Lolita, Nabokov refers to ‘Whistler's Mother,’ the well-known painting by James McNeill Whistler of his mother, which is titled Arrangement in Grey and Black (Lo 184). Likewise, The Real Life of Sebastian Knight could have been subtitled ‘Composition in Violet and White.’ The colour violet – or purple, which is the same hue but of a higher intensity – is encountered in the book in various forms, including ‘sugar-coated violets’, ‘violet sweets’, a pension called ‘Les Violettes’, ‘purple pansies’ and ‘violets’, ‘a mauve dress’, a ‘talc-powder tin with violets figured between its shoulders’, ‘an Oriental amethyst’ (purple or violet quartz), ‘a purple passage’, ‘purple facings’, ‘violet words’, ‘violet dark eyelids,’ and ‘violet-blue night-lamp’. There is also a plethora of flowers, either white flowers or flowers which have white varieties like ‘syringa’, ‘bluebell’, ‘lotus flowers’, ‘crocuses’, ‘roses’, ‘iris’, ‘bindwood’, ‘lilies’, ‘chrysanthemums’, ‘waterlily’, ‘carnations’, ‘pinks’, and ‘jasmin’. Violet or lilac can be obtained by mixing blue and red, as Nabokov learned at an early age from his mother who painted in watercolour for him (SM 36). In The Real Life of Sebastian Knight, this combination can be noticed frequently: the ‘sticky reds and blues’ from Sebastian's paintbox , the ‘blue water and scarlet wrists’ of a sunlit laundry, the ‘blue dragonflies’ which fly above a river whose bank is of ‘red clay’, and a ‘red and blue pencil’.

The novel contains the story of the endeavours of V., a young man of Russian extraction, to write a biography of his half-brother, Sebastian Knight, a successful writer. One theme concerns Knight's determination to establish himself as an English author, although his Russian is superior to his command of his adopted language. Another theme touches on the possibility that the deceased (in this case, Sebastian Knight, who died six months before V. started on his biography) can interfere with earthly life and can exert an influence on the actions of those who were nearest to him during his lifetime. Repeatedly, the presence of a ‘ghost’ is speculated on, and, most strikingly, on a number of occasions when Knight's novels foreshadow what would happen after his death. The loves of Sebastian form a third theme.