The Europeans created a number of good chances to break the deadlock in the first half, but failed to find the net and were made to pay for their profligacy after the break as Radamel Falcao and Victor Ibarbo helped Colombia to victory.
"Colombia are a great team," Vermaelen told Sporza. "Their movement is very dangerous and they are incredibly efficient in front of goal.
"They deservedly sit fourth in the FIFA ranking."
Vermaelen then went on to stress that the Belgium squad understands that it still has work to do ahead of the World Cup in Brazil.
"We always kept our feet on the ground after qualifying for the World Cup," he said. "We all know that there's still room for improvement. We still have plenty of work to do."
Belgium will be looking to return to winning ways on Tuesday when it hosts Japan.