A hard-fought 1-0 win at Newell's Old Boys saw Colon move level on points with Estudiantes, who were held to a scoreless draw at home to River Plate.
Estudiantes remain top on 25 points with their +6 goal difference, which is two goals better than Colon (25 points, +4).
At Newell's, Lucas Alario headed in the game's only goal on 76 minutes at the Estadio Marcelo Alberto Bielsa.
Marcelo Melli's well-weighted cross from the right found Alario's run and the striker found the bottom corner.
The goal came just two minutes after Newell's midfielder Lucas Bernardi had been sent off having picked up two quick yellow cards.
Newell's finished the encounter with nine men as Raul Villalba was sent off, while Leando Castillo saw red for the visitors.
Bottom side Arsenal were held to a 1-1 draw at All Boys and Argentinos Juniors' struggles continued with a 3-0 loss at Olimpo.
