Working as Haas&Hahn, artists Jeroen Koolhaas and Dre Urhahn splash color onto urban walls — and train young painters in the process.

It's an image seen around the world -- Praça Cantão, a square within the Santa Marta favela in Rio, blasted with stripes of rainbow colors that turn the jostling masonry walls into a brightly unified vision. Spurred on in 2010 by Dutch artists Jeroen Koolhaas and Dre Urhahn in collaboration with the local group "Tudo de cor para você", the painting was accomplished by 25 young people from the neighborhood, and reframed the square as a place of shared pride. The locals have since continued the project, with monthly painting task forces and other activities that have involved 800 people and transformed the aesthetic and the social psychology of the whole favela.

Known as "favela painters", Haas&Hahn have been working on community projects in Rio for almost 10 years. They've also worked in Haiti and Curaçao, and in 2011, they moved north into a tough neighborhood in northern Philadelphia, where they trained the Philly Painting crew to cover a worn-out commercial corridor in massive color blocks. They've returned to Rio in 2014 for a new project in the Vila Cruzeiro favela.

Community Improvement, TED Social Entrepreneurship, Artists,