
Ramos beat the offside trap to run onto a through pass from winger Fredy Guarin, round goalkeeper Leonel Moreira and put the Colombians ahead seconds before half-time.
Costa Rica had been reduced to 10 men after 27 minutes when forward Randall Brenes was shown a straight red card after a dangerous tackle on defender Luis Perea.
Colombia lead the group with three points ahead of hostsArgentinaandBoliviawho have one point each after their 1-1 draw on Friday in the tournament’s opening match in La Plata.
“The important thing was to start with a win and that’s what we did,” Ramos told reporters.
Substitute striker Hugo Rodallega had a chance to extend Colombia’s lead in the 54th but Moreira made another fine save.
The goalkeeper, asked if his performance had prevented a heavier defeat, said: “This is my job and I have my team mates’ back-up… we’re all fighting together and it’s not just the goalkeeper.”