from wiki....
Club Atlético de Madrid, S.A.D.
The Club was founded on 9 October 1939. A previous club was originally founded on 26 April 1903 as Athletic Club de Madrid by three Basque students living in Madrid. The founders saw the new club as a branch of Athletic Bilbao. In 1904 they were joined by dissident members of Real Madrid. They began playing in blue and white, as did Athletic Bilbao, but by 1911 they were playing in their current colours. The reason the club changed colours is not known for certain. However one theory is that red and white striped tops were the cheapest stripes to make because the same combination was used to make bed mattresses. The left over cloth was easily converted into football shirts. Although both Athletic Bilbao and Athletic Madrid started out with blue and white stripes, the discovery of a cheaper option probably persuaded them to change. The Madrid club did it first and they became known as Los Colchoneros—the mattress makers. Other more plausible account of the reason to change colours is that both Athletic Bilbao and Athletic Madrid used to buy Blackburn Rovers blue and white kits in England. Once in 1911 Juanito Elorduy, former player and member of the board of Athletic Madrid, went to England to buy kits for both teams. He did not find Blackburn Rovers kits and bought Sunderland red and white ones instead. Athletic Bilbao adopted Southampton full kit with red and white shirt and black shorts, whereas Athletic Madrid adopted the red and white shirt but kept Blackburn Rovers blue shorts.
First Atletico's ground, Ronda de Vallecas, was situated in the eponymous working-class area south of the city. In 1919, the Compañía Urbanizadora Metropolitana—the company that ran the underground communication system in Madrid—acquired some land, near the Ciudad Universitaria. As part of that project the company built a sports stadium, named Estadio Metropolitano de Madrid. With a capacity for 35.800 spectators, in 1923 it was rented by Atlético de Madrid, which used it until 1966 when they moved to the new Estadio Vicente Calderón. After the move, the Metropolitano was demolished, being replaced with university buildings.
Real Madrid and Atlético Madrid are clubs with contrasting identities and very different fates. Historically, Real Madrid have long been seen as the establishment club. On the other side, the Rojiblancos were always characterized by a sentimiento de rebeldía (a sense of rebellion) although, during the early Francisco Franco years, it was Atlético that was the preferred team of the regime, being associated with the military airforce, until the regime's preferences moved towards Real Madrid in the 1950s. That Franco's regime subsequently intervened to ensure success for Real Madrid for political and propaganda purposes is widely alleged and believed, although denied by many Real Madrid supporters.
Certainly, the dictatorial state sought to make political capital out of Real Madrid's European Cup trophies at a time when Spain was internationally isolated - "Real Madrid are the best embassy we ever had," said one minister.
Such perceptions have had an important impact on the city's footballing identities, tapping into the collective consciousness. In this vein, Atlético fans were probably the originators, and are the most frequent singers, of the song "Real Madrid, Real Madrid, el equipo del gobierno, la verguenza del país" ("Real Madrid, Real Madrid, the government's team, the country's shame").
http://en.wikipedia.org/wiki/Athletico_Madrid