Colle moved to Canada at a young age, and was educated at Carleton University. He worked as a teacher of history and economics for eighteen years, including several years at Michael Power High School and St. Michael's College School in Toronto.
His son Josh was elected to Toronto City Council in the 2010 election.
Colle served on the City of York municipal council from 1982 to 1985, and on the Metro Toronto Council as a York representative from 1988 to 1994. He was also chair of the Toronto Transit Commission from 1991 to 1994.
Colle was elected to the Ontario legislature in the provincial election of 1995, defeating incumbent New Democrat Tony Rizzo in the riding of Oakwood by about 1000 votes. In the provincial election of 1999, Colle defeated incumbent Progressive Conservative John Parker by about 9,000 votes in the redistributed riding of Eglinton—Lawrence. The Progressive Conservatives won both elections, and Colle sat in opposition during this period. In 1996, Colle supported Dwight Duncan's unsuccessful bid to become Liberal Party leader.
Colle championed environmental causes during his time in the legislature including the protection of the Oak Ridges Moraine. He was a co-chair of Mel Lastman's 1997 bid to become Mayor of Toronto. Lastman was also supported by prominent members of the Progressive Conservative Party in Toronto, and was opposed by members of the social democratic New Democratic Party.
The Liberals won the 2003 election, and Colle was re-elected by over 10,000 votes in his own riding. He served as a backbench supporter of the government of Dalton McGuinty. On October 23, 2003, he was named Parliamentary Assistant to Greg Sorbara, the provincial Finance Minister.
Colle was promoted to cabinet on June 29, 2005 as Minister of Citizenship and Immigration.
Colle was criticized for his role in giving out $32 million in government grants to immigrant and cultural groups without official applications or formal statements of purpose. In one case that the auditor general highlighted, the Ontario Cricket Association received $1 million when it asked for $150,000. Premier McGuinty agreed to commission a special report on the matter, to be released in July 2007. Colle was to appear before the Standing Committee on Estimates before the Legislature was prorogued by the Premier. Some believe this was arranged to prevent his testimony from going public.
On July 26, 2007, Colle resigned as Minister of Citizenship and Immigration. Gerry Phillips was sworn in as the new Minister of Citizenship and Immigration, in addition to his responsibilities as Minister of Government Services.
In October 2007 he was re-elected to serve his fourth term to represent the Eglinton-Lawrence riding. During this term he has held two senior positions in the party. From October 2007 to February 2010 he was Chief Government Whip. He served as Parliamentary Assistant to the Minister of Community Safety and Correctional Services from February 2010 to December 2010. In December 2010, he was appointed as the Parliamentary Assistant to the Minister of Children and Youth Services.
On February 24, 2009, Colle introduced the Zero Tolerance to Violence on Public Transit Act, 2009 in an attempt to address the growing incidence of gun violence on Toronto Public Transit.
On March 25, 2009 Colle appeared to buck his own party by introducing Bill 160: The Caregiver and Foreign Worker Recruitment Act, 2009. This was in response to a Toronto Star expose on the abuse of foreign nannies. After some initial reluctance by the government, Colle was able to convince the Labour Minister and the government to intervene to stop the abuse. The government committed to introducing legislation to license "nanny brokers", ban placement fees, and post licensed placement agencies on an online registry.
The McGuinty government introduced Bill 210, Employment Protection for Foreign Nationals Act (Live-in Caregivers and Others), 2009 (EPFNA) on October 21, 2009 and passed the "Nanny Protection Act" on December 15, 2009.
In 2010, Colle took on the issue of bedbugs eventually convincing Health Minister Deb Matthews to provide $5 million to fight the scourge with a bedbug strategy.
Colle also spent most of his fourth term advocating to get the Eglinton Crosstown LRT built. The provincial government has committed $8 billion for the new Eglinton line that runs along the southern border of his riding of Eglinton-Lawrence. He has been on a personal crusade to get the Crosstown built ever since the Harris government cancelled the Eglinton subway in 1996 even after the tunnel was dug.
In October 2011 he was re-elected to serve his fifth term to represent the Eglinton-Lawrence riding. He was appointed as the Parliamentary Assistant to the Minister of Transportation and the Minister of Infrastructure. During this term Colle organized a petition requesting that a station on the Eglinton Crosstown LRT line be added at Oakwood Avenue.
In June 2014 he was re-elected to serve his sixth term to represent the Eglinton-Lawrence riding. He serves as Parliamentary Assistant to the Minister of Transportation. He was also appointed as Deputy Government Whip.
In March 2016 Colle tabled the Tomato Act, proclaiming the tomato as the official vegetable of Ontario (despite it being technically a fruit) and designating July 15 as Tomato Day.