With Lanus knocking off the former leaders 1-0, Estudiantes and San Lorenzo defeated Argentinos Juniors and All Boys respectively to join Colon on 21 points.
Estudiantes edged out Argentinos Juniors 1-0 on Monday thanks to Juan Manuel Olivera's late goal with the La Plata-based club extending their unbeaten run to eight matches.
The advanced midfield trio of Juan Sebastian Veron, Patricio Rodriguez and Joaquin Correa gave Estudiantes the ascendency in the first half, while Argentinos Juniors suffered an early blow away from home when striker Leonardo Pisculichi came off injured in the 21st minute.
The hosts created more genuine goal-scoring opportunities after the break but had to wait until the 80th minute to beat Argentinos Juniors goalkeeper Nereo Fernandez.
Franco Jara's cross from the right found Leonardo Jara, who headed down to Guido Carrillo and although the striker's bicycle kick was saved by Fernandez, Olivera was there to convert the rebound.
The win took Estudiantes to second position in the table with 21 points.
Estudiantes sit above Colon on goal difference but trail San Lorenzo on goals scored.
Colon lost at Lanus on Saturday with Victor Ayala scoring the only goal of the game for the home side in just the second minute.
San Lorenzo claimed the overall lead with a come-from-behind 2-1 triumph at All Boys on Sunday, thanks to late goals from Mauro Matos and Walter Kannemann.
Javier Campora gave All Boys the lead in the first half and, despite some nervous moments after the break, the hosts looked set to hold on for their first win in four matches until San Lorenzo struck with seven minutes remaining.
Nestor Ortigoza produced a pin-point chip over All Boys' defence to find Matos and the substitute finished underneath goalkeeper Nicolas Cambiasso, while in the 88th minute, Kannemann stole victory with a header from Angel Correa's corner.
The top four clubs heading into Round 12 all lost, with Velez Sarsfield (20 points) dropping from second to fourth after going down 1-0 to Racing Club.
River Plate (20) conceded in the 85th minute to lose 2-1 at Belgrano to finish the round in fifth, while Boca Juniors thrashed Godoy Cruz (19) 3-0 to send their opponents to sixth in the table.
The win - Boca's first in five games - took the Buenos Aires giants up to ninth with 18 points, just one point behind eighth-placed Lanus.
In other results in Argentina's top tier, Rosario Central defeated Newell's Old Boys 1-0, Atletico Rafaela drew 2-2 with Quilmes and Tigre won 1-0 at Arsenal.
