Colback told the club's official website: "The winning goal was difficult to take, especially after we'd just had a couple of chances ourselves.
"I don't think it was a great game. Reading are fighting for their lives and it was always going to be tough.
"We had some opportunities – Alfie [N'Diaye] went through on the keeper, who then made a good save on Danny – so to lose it after that was very disappointing."
Sunderland are now 12th in the Premier League on 29 points, eight points clear of the relegation zone.