He painted, in oils and in watercolours, the landscapes of the Campagna Romana and the Agro Pontino; he was a collector, grower and painter of orchids.

[2][note 1] He was the fourth child of the English painter Charles Coleman, who had come to Rome in 1831 and settled there permanently in 1835, and of a famous artist's model from Subiaco, Fortunata Segadori (or Segatori), whom he had married in 1836.

Following the mocking reception of Una mandria di bufali nelle paludi pontine, a naturalistic painting of a herd of buffaloes in the Pontine marshes, at the International Artist's Club in 1872,[2][6] he reportedly began to paint genre subjects in the manner of the then-fashionable Mariano Fortuny, although no works showing the influence of the Spanish painter are known.

[7] At the instigation of Nino Costa, he soon returned to the depiction of the people, animals and landscapes of the Campagna Romana and the Agro Pontino.

[2] In 1885, Coleman was among the founding members of the group In Arte Libertas, of which Nino Costa was the leading force and the other founding members were Vincenzo Cabianca, Onorato Carlandi, Giuseppe Cellini [it], Alessandro Castelli [it], Cesare Formilli [it], Giuseppe Raggio, Alessandro Morani, Alfredo Ricci, Mario de Maria and Gaetano Vannicola [it].

[8][note 3] Coleman had six paintings in the first exhibition of the group, which took place from 10–28 February 1886, in the studio of an amateur painter named Giorgi, at 72 via S. Nicola da Tolentino.

[5] The club published his panorama of the Gran Sasso d'Italia in 1884,[16] and awarded him a gold medal at the Esposizione Alpina, or mountaineering exhibition, in Bologna in 1888.

[2] Later the same year, he was the only artist to have a whole room dedicated to him at the Esposizione internazionale d'arte in Rome,[17][18] in which forty-nine of his works, both oils and watercolours, were hung by a group of his friends.