Light and darkness (the colours black and white), youth and age, reality and fantasy, all play a part here, but certainly the most important are light and darkness. Krapp (what a name!) has 'rusty brown' trousers and waistcoat, but a 'grimy white shirt' and a white face; the stage is in darkness apart from the lit desk; the thirty-five-year-old Krapp lived with Bianca in Kedar (Hebrew for 'black') street; the younger Krapp remembers seeing a woman, 'all white and starch' with a 'black hooded' pram; the white dog has a black ball, and so it goes on, with the light and the dark sometimes blended, as with the younger Krapp shielding his woman from the the sun.
The eyes of women are a theme too: Bianca's are 'incomparable'; the woman with the pram has eyes 'like chrysolite' (recalling a word used in Othello); the eyes of the woman Krapp shields were 'just slits' in front of the glare of the sun, although they opened in shadow; Krapp's last tape records 'The eyes she had!'. In such a short play there are a number of characters, but all come from only one man.
This is a book of memory, therefore time, and we can feel it in the movement not only of the tape spool revealing the past but also, in its unwinding, Krapp's delight in saying 'Spooool', his joy of words in themselves, another example being him forgetting the meaning of 'viduery', searching in the dictionary, finding the word and also the name of the 'vidua' bird, the sound of which he relishes.