In 1954, Castella won the Union Méditerranéenne for Modern Art prize, which enabled him to stay in Nice, where he returned with many studies and paintings. He formed a close friendship with artists Lachièze-Rey and Adilon and spent time with them at the Villa Zoé, an artists' residence in Nice, from 1954 to 1955. That same year, Castella participated for the first time in the Salon du Sud-Est in Lyon and collaborated with the Drouant-David gallery in Paris until 1956.
In 1955, he also took part in the Biennale of Menton. During this period, his work was figurative, featuring familiar scenes such as beaches, still lifes, portraits, landscapes, and the sea, rendered in a thick, textured material, with half-tones and a great sense of luminosity. Although his painting was similar to that of his friends Adilon and Lachièze-Rey, it stood out for its own unique originality.