West Yorkshire Police said: "It is vital that we find him as a matter of urgency and reunite him with his family".
Colin is thought to be wearing a blue fleece, grey pyjama bottoms and a dark coloured beanie hat.
He was last seen near Dewsbury Minster at around 6.01am on Sunday, 17 November.
He is approximately 5ft 7ins tall and of slim build.
Police officers are continuing their searches today around the Wilton Bridge/Horbury Bridge area, West Yorkshire Police confirmed.