Sagrada Família, designed by Antoni Gaudí, is representative of Catalonian modernist architecture, and is still an ongoing project, nearly 140 years after construction began in 1882. The Façana del Naixement was originally intended to be colored, but it has not been completed after Gaudí’s death, and the pattern and design of the coloring is unknown. This work proposes a new possibility to resolving this issue using AI. When coloring complex forms, Gaudí often used a method called trencadis – breaking ceramic into small pieces and putting them together in a kind of mosaic. The AI used for this piece is called “Langton’s Ant” and is a kind of cellular automaton, constructed by a discrete model that simulates an ant moving in grid-like cells according to local rules. The AI creates examples of mosaics in cells, using the 7 colors, or 6 tones, of Gaudí’s coloring style, and the work displays rich decoration like a complex phenomenon of life. It is sustainably recoloring the construction as though it were an architect producing through trial and error.