The actresses only read the script once. Abdellatif Kechiche insisted that they forget what the script said line for line, and instead asked them to improvise their scenes and really let their actions and words come out naturally and as unforced as possible.

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There was no makeup artist and hairstylist on the set. The actresses were not allowed to wear makeup for most part of the movie.

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For the first time ever the Palme d'Or at Cannes was also officially awarded to two of the actors. Usually only the director gets the distinction.

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A good portion of the B-roll footage with Adèle Exarchopoulos that ended up being used are in fact of the actress when she was out of character. The camera would be on her when she ate and even when she slept on the train while they were on their way to set. Since during this footage people kept calling Exarchopoulos by her first name instead of Clementine (the original name from the graphic novel), they agreed to have the main character's name changed to Adèle.

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Adèle Exarchopoulos was 18 and Léa Seydoux was 26 at the time filming began.

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In preparation for her role as Emma, Léa Seydoux attended painting and sculpture lessons. She also undertook extensive reading on arts and philosophy, and visited museums before filming began. To assist her in portraying the masculine characteristics of the arts student role, the director requested Seydoux to go for training sessions to tone up her physique and also study the films of Marlon Brando and James Dean to learn their traits.

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The film was considered a front-runner for an Oscar nomination for Best Foreign Film upon its release and success at the Cannes Film Festival. However, the film was deemed ineligible by the Academy Awards due to its late release in France.

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The walk-by scene took 100 takes.

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The first film adaption of a graphic novel to win the Palm D'Or.

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The first scene the actresses shot together was Adèle's dream sequence.

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Both Adèle Exarchopoulos and Léa Seydoux were put in acting classes as children by their parents to help overcome shyness.

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Léa Seydoux refused to have her character's name be changed to her own name as one of the conditions she had for playing the part of Emma. Among these other conditions are: she will not smoke real cigarettes because she has quit smoking two years before, she will not have real sex on camera, and she will not wear her own clothes for the film. Apart from these, she was willing to do anything that Abdellatif Kechiche will require her for any of the scenes.

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The main characters refer to and discuss the writings of Sartre; particularly "Dirty Hands" and "Existentialism is a Humanism".

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Adèle Exarchopoulos and Jérémie Laheurte started dating on the set.

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At Cannes, the film shocked some critics with its long nd graphic sex scenes (although fake genitalia were used), leading them to state that the film may require some editing before it is screened in cinemas. Several critics placed the film as the front-runner to win the Palme d'Or and it went on to win the coveted prize. The judging panel, which included Steven Spielberg, Ang Lee and Nicole Kidman, made an unprecedented move to award the top prize to the film's two main actresses along with the director. Jury president Spielberg explained: "The film is a great love story that made all of us feel privileged to be a fly on the wall, to see this story of deep love and deep heartbreak evolve from the beginning. The director did not put any constraints on the narrative and we were absolutely spellbound by the amazing performances of the two actresses, and especially the way the director observed his characters and just let the characters breathe."

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Abdellatif Kechiche developed the premise for Blue Is the Warmest Colour while directing his second feature film, L'esquive (2003). He met teachers "who felt very strongly about reading, painting, writing" and it inspired him to develop a script which charts the personal life and career of a female French teacher. However, the concept was only finalised a few years later when Kechiche chanced upon Julie Maroh's graphic novel, and he saw how he could link his screenplay about a school teacher with Maroh's love story between two young women.

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Léa Seydoux said that in hindsight Abdellatif Kechiche hired her because of her upper class background since her character hails from an upper middle class family to serve as contrast to the protagonist's blue collar background. She explained further that Kechiche gravitates to unknown actors and actresses and that there has to be a deeper reason why he did his unprecedented move of casting a more known actress for his film

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A lot of the footage has Adèle Exarchopoulos' character being called Adele and a lot of the actors end up using her name for the scenes because of the natural acting that the director preferred. Abdellatif Kechiche then proposed to Adèle Exarchopoulos that the character be named after her.

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A scene in which Adele's parents walk in on her and Emma in bed together and kick them out of the house was filmed, but ultimately cut out of the theatrical cut. This explains why Adele is all of a sudden living with Emma half way through the film.

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Adèle Exarchopoulos has often said that the breakup scene was the most difficult scene to shoot, far more than any of the sex