At the 2018 Visegrad Film Forum, cinematographer Slawomir Idziak claimed that the script and initial cut of this film focused on the journalist character (played by Hélène Vincent) and her efforts to investigate the authorship of the unfinished musical composition that drives the plot. It was only during the editing process that director Krzysztof Kieslowski re-structured the film to focus on Julie (played by Juliette Binoche).
When Olivier has tracked down Julie but is then ignored by her, there is a close-up of Julie allowing a sugar cube to soak up her coffee. Deeming that the sugar cube had to soak up the coffee in precisely 5 seconds, Krzysztof Kieslowski had his assistant director test multiple brands (which soaked with coffee anywhere from 3 to 11 seconds) to find one that took just the correct time.
Fade-outs in this film, which are traditionally used in movies to represent time passing or to conclude a certain scene, instead bring the viewers back to the point in time in which the fade-out began. The occasional fade-outs and fade-ins to Julie's character are used to represent an extremely subjective point of view. According to director Kieslowski: "at a certain moment, time really does pass for Julie while at the same time, it stands still. Not only does her music come back to haunt her at a certain point, but time stands still for a moment."
At one point, we see Julie carrying a box which, as a close-up shows, has prominently written across it the word "blanco", Spanish for white; in the next shot we are looking at her from behind, and she pauses in the street as a man in blue passes her on her left and a woman in red passes her on her right. This is a subtle reference to the structure of the Three Colours trilogy - blue, white, red, in that order, mirroring the French flag. In another scene, children in red and white bathing suits run out and jump in the blue swimming pool.
After the opening screening of this film at the 2018 Visegrad Film Forum in Bratislava, cinematographer Slawomir Idziak described an unusual technique he used to shoot the scene where blue light glares appear superimposed over Juliette Binoche's character. It was apparently achieved by wrapping the camera in blue gels, opening its rear and flashing lights directly at the film negative.
Zbigniew Zamachowski, Julie Delpy: the stars of the sequel Trois couleurs: Blanc (1994), make appearances in this film.