The 17-year-old defender, who is regarded as one of the best youth prospects in Scotland, will train at United base Carrington with a view to winning a contract.
"Coll was watched by Man United in a couple of reserve games and Martin Ferguson wondered if they could have a look at him," Nixton told reporters.
"They're looking after him and he'll train with them before they decide what they want to do. It's a fantastic opportunity for the boy.
"No matter what happens in the end, it will let him see what's out there and he'll train in fantastic surroundings at Carrington."
A host of Premier League clubs are also believed to be monitoring proceedings.