A fourth-minute penalty saw Colon edge Tigre 1-0 and that – along with Estudiantes' 1-1 draw – helped them move clear after nine games.
At Colon's Estadio Brigadier Estanislao Lopez, the hosts earned a penalty in the second minute when Martin Luque was brought down by goalkeeper Javier Garcia.
Luque's strike partner Lucas Alario stepped up and sent Garcia the wrong way from the spot, putting his effort into the bottom corner.
That win on Friday put the pressure on Estudiantes a day later, and they conceded a late goal at Velez Sarsfield.
They had looked on track for three points at the Estadio Jose Amalfitani as Guido Carrillo headed in a Mauricio Rosales cross at the back post just 38 seconds into the second half.
But Velez, who sit fourth, levelled through a stunning goal from substitute Jorge Correa on 88 minutes.
Correa was found by Lucas Pratto in a pocket of space and, after his first touch led to a bouncing ball, his 30-yard effort was unstoppable.
Former Lazio and Inter striker Mauro Zarate almost snatched all three points for Velez but his effort was well kept out by Estudiantes goalkeeper Jeronimo Rulli.
Godoy Cruz sit three points behind leaders Colon after Mauro Obolo's double led them to a 2-1 win at home to Arsenal.
Elsewhere, River Plate bounced back to winning ways with a 2-0 victory over Lanus and Olimpo overcame Atletico Rafaela 2-1.
Late goals from Osvaldo Barsottini and Luis Peralta helped Gimnasia La Plata to an upset 2-1 win over San Lorenzo.
Newell's Old Boys and Argentinos Juniors were unable to be separated in a 0-0 draw, while the clash between Quilmes and Boca Juniors also finished goalless.
Rosario Central beat a 10-man All Boys 2-0 and Racing Club were 2-0 victors at home to Belgrano.
