Van Amersfoort Racing rookie Colapinto, who took pole for the feature race in Bahrain, took his maiden series win after a much-interrupted race.
Having started on pole in the reverse-grid sprint, he lost the lead to Collet on lap four when the MP Motorsport driver took advantage of DRS on the main straight.
Colapinto held on to second place throughout, but was able to regain the lead from Collet on the run to the Tamburello chicane beginning the final tour after a virtual safety car period had ended.
Seconds later, Collet’s race was dramatically ended after he made contact with Isack Hadjar, who had positioned his car to the Brazilian's outside approaching the left-hander.
Both cars ended up in the gravel, although Hadjar emerged from the gravel to finish fifth, as Victor Martins (ART Grand Prix) just held off Prema's Jak Crawford for second at the line.
Colapinto had a good start off the line, with second-place starter Ido Cohen getting swallowed up by Kush Maini and Collet on the run down to Turn 1.
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Hadjar swiftly took fourth from Martins at Tamburello on lap four, before taking Maini for third at the Villeneuve chicane three laps later.
The first safety car was deployed on lap nine after Zak O’Sullivan went off at Turn 6, shortly followed by Pepe Marti in a separate incident.
Racing resumed on lap 11, with Maini taking a drive through penalty for being outside his grid box at the start. That dropped him out of podium contention and promoted Crawford to fifth place.
The safety car was promptly deployed for a second time after Reece Ushijima and Federico Malvestiti collided exiting Tamburello, the Van Amersfoort driver mounting the back of his Jenzer rival before both ended up in the gravel.
Cohen's race went from bad to worse, the Israeli forced to pit for a new front wing after making contact with Kaylen Frederick on the restart.
The lights went green again on lap 17, with Collet holding onto the lead from Colapinto, before Arthur Leclerc wiped out the 150-metre board at the exit of Villeneuve, prompting a virtual safety car.
Colapinto was right on Collet's gearbox when the race restarted and duly took the lead on the last lap before Collect and the pursuing Hadjar collided.
Behind Martins and Crawford, Roman Stanek also took advantage of the incident to take fourth place for Trident, with his feature race polesitting team-mate Zane Maloney following the recovering Hadjar home in sixth.
Oliver Rasmussen finished seventh in his first race of the season, having replaced Jonny Edgar at Trident, while Frederick managed to emerge from the collision with Cohen unscathed to take eighth.
Leclerc, who had risen as high as 12th at one point after contact in qualifying with Enzo Trulli left him 21st on the grid, reached the finish in 14th.
