[Ended]

"He was tall and muscular, a blue-collar type"

A blue collar worker is lower class by definition. As phrased above, the "tall and muscular" bit is part of the writer's observation/stereotype that the man is a blue collar worker. "He was big and strong and (therefore) looked like someone who works in manual labour".

[yummyfajitas]

Blue collar is manual work which is not the same thing as lower or lower middle class.