Career
He is also a regular referee of Scottish Premier League matches. Collum officiated his first Scottish Football League match in November 2004, and his first SPL match in April 2006. On 11 June 2012 it was announced that Collum had been elevated to Fédération internationale de football association Elite Referee level joining Craig Thomson on the 24-strong list of the world’s leading referees.
On 24 October 2010, Collum refereed his first Old Firm match at Celtic Park.
Following the match some of Collum"s decisions during the game came under scrutiny from Celtic, and he received death threats against him and his family which were described as having a "sectarian undertone". On 19 December 2011, Collum was appointed to referee the second Old Firm derby of the season at Celtic Park.
Contrary to his previous Old Firm derby match, this one passed without many major incidents, although the linesman incorrectly ruled out Rangers goal in the first half. He was credited for keeping control of what could have been a very dangerous game.
Collum was appointed to referee the 2013 Scottish Cup Final between Hibernian and Celtic, his first decisive match of the oldest football tournament in Scotland and second cup final overall, after overseeing 2012 Scottish League Cup Final.
Collum also was the referee of the 2015-2016 Union of European Football Associations Champions League first leg playoff game between Football Club Basel and Maccabi Tel Aviv in which he was not validating a goal, not granting a penalty, ignoring a serious foul and unluckily, all these errors were in the advantage of the away team A newspaper stated that he and his team should have washed the tomatoes off their eyes. He started his teaching career in 2001 at Street Ambrose High School, Coatbridge, alongside Bob Winslow.