Liam Kelly had fired Killie ahead, but Colvin pointed to the spot after Dougie Imrie fell in the box under Mark O'Hara's challenge and Paul McGowan converted the penalty.
But Shiels was careful not to hit out at the official, and called for referee's to be questioned over controversial decisions.
"I have to watch what I say, Mark was unlucky. Lets put things into perspective, I'm the manager of Kilmarnock and I'm going to be biased towards my team," said Shiels.
"If you want me to speak about decisions in a game then interview the referee, I will talk all day long in response to what he has said.
"That's the way it should be, I will not answer questions about referees and I'm emphatic about that. I'm not doing any more interviews until the referees are interviewed.
"The conditions were really difficult for both teams and I was very pleased with the performance, we were in control of the game, but it was taken out of our hands - the penalty changed the whole shape of the game."