Detectives said he suffered a “violent” death in the early hours of Tuesday morning, sparking a murder hunt.
In an emotional statement, his mother, Anne Gray, said the news had deeply affected the family, which had already been hit hard by the death of Mr Armstrong’s twin brother.
She paid tribute to her son, saying his death will leave “a huge hole”.
The body of 49-year-old Colin was found dead in a house in Greenmill Brae, Macmerry.
His mum said: “Colin was a loving, gentle, harmless, friendly but very private man, who was a much-loved son and brother of a family, now devastated by his death. Colin was left badly affected by the death of his identical twin brother, Stephen, who died from cancer in 2009.
“Now Colin has been cruelly taken from us, this tragedy leaves a huge hole in me and my family. He will be sorely missed, but always remembered by all who knew him.”
Mr Armstrong, who was originally from Musselburgh, had only recently moved to Macmerry from Dunbar.
He lived just a few doors down from the house where his body was discovered. He is understood to have suffered multiple stab wounds.
Locals described Mr Armstrong as a “quiet, friendly” man who would always stop and speak to his neighbours.
The fatal attack happened on the same street where a 30-year-old man was seriously injured after being stabbed in September 2012.
However, residents said serious incidents were extremely unusual in the quiet housing estate. Mr Armstrong’s body was found at around 1.20am on Tuesday. Police said they were alerted to his death by the ambulance service, who had been first on the scene. The murder probe is continuing, and police are keen to gather more information about a light-coloured, old-style Honda Civic which is believed to been near the crime scene around the time Mr Armstrong’s body was found.