Black Collar Worker: It is used to refer to workers in the mining or the oil industry or sometimes also used to refer to people who are involved in black marketing activities.


List of Collar Workers
https://www.jagranjosh.com/general-knowledge/list-of-collar-workers-1404546729-1

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Black collar - Manual laborers in industries in which workers generally become very dirty, such as mining or oil-drilling;[unreliable source?] has also been used to describe workers in illegal professions.


Designation of workers by collar color
https://en.wikipedia.org/wiki/Designation_of_workers_by_collar_color

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Black-Collar Worker - is used to referring to workers in the mining or the oil industry. Sometimes, it is also used to refer to people who are employed in black marketing activities.


Types of Collar Workers! (updated)
https://www.linkedin.com/pulse/whats-types-collar-workers-hassan-choughari/

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The term -black collar- is used here because it used to refer to those whose collars become black by the nature of their jobs. While it has now taken on a new meaning, it was once used to label those with jobs as coal miners, oil workers, and other similar positions.

Now, black collar workers are the creative types of professionals like artists, graphic designers, and video producers. The moniker has transferred over to them due to their unofficial uniforms, which are generally comprised of black attire.


Complete Collar Colors: Understanding Consumer Personas
https://klcampbell.com/complete-collar-colors-understanding-consumer-personas/