*Club domestic league appearances and goals, correct as of 20:44, 22 December 2024 (UTC) ‡ National team caps and goals, correct as of 8 September 2023
Born in Vimercate, close to Milan, Colombo is a product of the youth academy of AC Milan. His goal tally in the club's youth teams led to him making his debut for the Primavera (under-19) side at the age of 15. Due to minor injuries, his time in the Primavera was cut short.
Due to the COVID-19 pandemic in 2020, the Milan first team's lack of striking options meant they were unable to cope with the busy schedule after football resumed, and Colombo was promoted to the senior side. He made his first-team debut, aged 18, on 12 June 2020, replacing Lucas Paquetá after 82 minutes in a 0−0 draw at home to Juventus in the Coppa Italia.[3] He made his Serie A debut in a 5−1 home win against Bologna on 18 July 2020.[4][5]
On 5 September 2020, he scored his first senior goal in a 4–1 win against Monza in a friendly match.[6] On 24 September 2020, he scored his first goal in official competition, during a Europa League match against Norwegian club FK Bodø/Glimt.[7]
Loan to Cremonese
On 26 January 2021, Colombo joined Serie B club Cremonese on a six-month loan, until the end of the season.[8]
Loan to SPAL
On 31 July 2021, Colombo was sent to Serie B club SPAL on a one-year loan.[9]
Loan to Lecce
On 7 July 2022, Colombo joined recently promoted Serie A club Lecce on a one-year loan, with an option to be signed permanently.[10]
Loan to Monza
On 1 September 2023, Colombo moved on a one-year loan to Monza.[11]
Loan to Empoli
On 31 July 2024, Colombo joined fellow Serie A club Empoli on a season long loan with the option to make the deal permanent.[12][13]