The movie begins with Kadhir(Tamil version), Ravi(Telugu version) (Ravi Krishna) on his way to work. People stare at him and laugh behind his back as he travels to his office. He appears distracted throughout the day and even instructs his assistant to postpone an important meeting with a big client. He then waits for someone at the beach with a bouquet of flowers. His best friend, Lakshmi (Suman Setty) sees him and asks him who he is waiting for her. Kadhir explains he is waiting to meet his girlfriend, Anita (Sonia Agarwal) for their date. In flashbacks, we are shown how Kadhir first met Anita.
Kadhir belongs to a lower middle class family, living with his parents and younger sister in Rainbow Colony. He is perceived as a good for nothing person as he skips classes, fails in exams, and gets involved in fights. Kadhir believes that his father Vijayan hates him and often quarrels with him, even threatening to leave the house, only to be persuaded not to do so by his mother Sudha. Kadhir's life changes when a Hindi speaking North Indian family moves into the same colony. Kadhir is attracted to the daughter to his new neighbours' daughter, Anita. Although he tries to woo her, Anita treats him with disdain. One day, Kadhir confesses to Anita that he loves her. He tells her that having always been ridiculed, he found respite in the fact that she at least bothered to look at him. He promises to wipe her thoughts out of his mind, as he is not right for her.
Despite himself, Kadhir continues pursuing her. Anita realizes that Kadhir is not such a useless fellow when Lakshmi tells her that he can dismantle and assemble a motorcycle within minutes. Anita takes Kadhir to a Hero Honda dealer and asks them to give him a job. He is promised a job if he can assemble a bike. Initially, the lethargic Kadhir is disinterested and gives up the task. Anita takes him to a corner and spanks him before revealing that she has fallen in love with him. She then tells him that they can only be together if he gets a proper job and gets his life straightened out. Kadhir then demonstrates his skill in motorcycle assembly, securing a job with the dealer.
Later that evening, Kadhir plans a treat for his friends. However, Anita confronts him and makes him break the good news to his parents first to get their blessings. However, Kadhir's father berates him as usual for getting a job instead of completing college. Then later at night, Kadhir overhears his father telling his mother how proud he is of their son since getting a job with such a prestigious company is not easy. Only then does Kadhir realize his father's love for him and weeps in joy.
The intimacy between Kadhir and Anita is discovered by her mother and she refuses to permit their marriage even as Kadhir's father tries to persuade her otherwise. Anita's family is heavily indebted to another Northern Indian family that has been supporting them since Anita's father suffered losses in his business. Anita's parents want Anita to marry the son of the family that has helped them.
Anita escapes her home and meets Kadhir and they end up in a hotel room. Anita reveals that she has made the biggest decision of her life by deciding to make love to him, as he should not regret falling in love with her when she marries the man her parents chose. Though stunned by her decision, Kadhir goes with her plan and the two consummate their love. The next morning Kadhir and Anita argue when Kadhir says he wants Anita to live with him, while Anita accuses him of being attracted to her only because of the sex. They continue arguing as they exit the hotel. While crossing the road, Anita is knocked down by a truck as a helpless Kadhir watches. Kadhir is also hit by a speeding vehicle. Anita dies on the spot and he tries to commit suicide only to be helped by a group of nuns. Kadhir then hallucinates about Anita's spirit coming to him and advising him to live life to the fullest.
Back in present day, it is revealed that Kadhir has indeed become successful in life but has remained mentally damaged since Anita's death. He still believes she is alive and always imagines talking to her. The film ends with Kadhir talking to himself at the beach, thinking he is talking with Anita.Ravi Krishna as Kadhir (Ravi in Telugu version)
Sonia Agarwal as Anitha
Suman Setty as Lakshmi Narayanan
Vijayan as Kadhir's father (Tamil version)
Chandra Mohan as Ravi's father (Telugu version)
Sudha as Kadhir's mother
7G Rainbow Colony was the second venture of Selvaraghavan as a director. He revealed that the film's inspiration came from his college days when he had been fascinated with a Punjabi girl during his education in KK Nagar. He based several of the scenes on real-life happenings with his friends, revealing that the film was "75% biographical" and the lead character was an "average guy" like himself, who "no one would make a film on". Selva cast Ravikrishna, son of producer Rathnam after a successful screen test. For the lead female role, Selvaraghavan initially considered Genelia D'Souza and auditioned Mumbai model Mamata, who was to work with Dhanush in Sibi Chakravarthy's shelved film Raghava, before selecting Sonia Agarwal due to her Punjabi origin.
Selvaraghavan teamed up once again with musician Yuvan Shankar Raja after Thulluvadho Ilamai and Kaadhal Kondein. The soundtrack released on 21 May 2004 and features 10 tracks overall, two of which are Instrumentals. The lyrics were penned by Na. Muthukumar. Yuvan Shankar Raja used live music for the score, for which he worked with a 40-piece orchestra for one month. As it was the case with Kaadhal Kondein, an "Original Soundtrack", consisting of 25 tracks, which are pieces of the film score and were titled as "Theme Music", was released afterwards. It includes one bit song "Idhu Enna Maatram" (Theme Music 14), sung by legendary singer P. B. Sreenivas. Yuvan Shankar Raja has given a Madhuvanti in "Kanaa Kaanum Kaalangal".
Composer Yuvan Shankar Raja received universal critical acclaim for the musical score as the songs and the film score were hailed as "excellent" and the album as a "great" and "must buy". Particularly, the instrumental track in the album was very much lauded, described as "highly innovative" and "eminently haunting" and even hailed as "one of the most haunting instrumental tracks ever". The song became very popular and were topping the charts for some time. Yuvan Shankar Raja received his first Filmfare Best Music Director Award in Tamil for the music, at the age of 25, becoming the youngest composer ever to win this award till 2011 when GV Prakash Kumar won Filmfare Best Music Director Award in Tamil for his work in ,Aadukalam
All music composed by Yuvan Shankar Raja.2004: Filmfare Best Music Director Award (Tamil) - Yuvan Shankar Raja
2004: Filmfare Best Male Debut (Tamil) - Ravi Krishna
The film opened in 92 screens throughout Tamil Nadu and expanded to 118 prints. Made on a budget of ₹3 crore, it turned profitable in first week grossing ₹6.27 crore selling 2 million tickets !
The film was simultaneously made in Telugu and simultaneously released as 7G Brundavan Colony. The only difference with the Tamil version was that the lead character was named Ravi instead of Kadhir, and that the role of the protagonist's father was played by Telugu actor Chandra Mohan. The song "Thalachi Thalachi" known as "Ninaithu Ninaithu Parthel" in the Tamil version had a shorter duration as compared to the Telugu version.