Surprise package Lanus stay top in Argentina
The unfashionable side from the sprawling southern suburbs of Buenos Aires went ahead in the 56th minute when Diego Valeri scored from close range after a neat combination with Diego Lagos.
Two minutes later, Cristian Menendez rounded goalkeeper Diego Pozo to score the second.
German Rivarola headed one back for third-placed Colon in the 73rd minute after a mistake by Lanus goalkeeper Carlos Bossio but the visitors had Alejandro Capurro sent off nine minutes later as they lost for the first time in the championship.
Lanus have 15 points from six games, four ahead of Velez Sarsfield who host River Plate on Sunday, and Colon.
Gimnasia-La Plata lost 1-0 at home to Tigre when midfielder Martin Morel curled in a free kick four minutes from time.
Estudiantes, who are without a coach after Leonardo Astrada quit on Wednesday, continued their poor run as they lost 1-0 at San Martin-Tucuman, Maximiliano Velasquez heading the only goal early in the second half.