The 21-year-old scored his side's third goal after converting from the spot in the 83rd minute, after Martin Erlic and Dimitris Nikolaou scored for Spezia in the 39th and 45+3 minutes.
Michael Folorunsho scored the only consolation goal for Italian Fourth Division side Pordenone after converting from the spot in the 51st minute.
The Serekunda-born player marked his introduction at the Liguria-based team in Italy after scoring his opening goal just a week after he signed for the club.
The Gambian international signed a one-year loan deal with Spezia with an option and counter-option from Atalanta Bergamasca Calcio.
He was last season loaned to Hellas Verona, where he scored 2 goals in 25 appearances.
Colley started playing for Atalanta's under-19 squad in the 2017–18 season.
He made his professional debut for the senior team in a 1–2 Serie A loss to Bologna on 15 December 2019, before being loaned to Hellas Verona last season.
Colley made his debut for The Gambia national football team on 22 March 2019 in an Africa Cup of Nations qualifier game against Algeria, as a 81st-minute substitute for Ebrima Sohna.
Ebrima Colley and Spezia opened their Serie A campaign away to Cagliari yesterday, Monday.