It doesn't answer your question but here is a good example of how the term "blue-collar" is used: https://www.kirkusreviews.com/book-reviews/e-e-lemasters/blue-collar-aristocrats-life-styles-at-a-workin/ "Blue-Collar Aristocrats: Life Styles at a Working-Class Tavern" "Masters' subjects are workers in the construction industry, the 'blue-collar aristocrats' who make good bread (at least they did before the current depression), like to fish and hunt with their chums and spend evenings shooting pool. The most conspicuous thing about them is their hostility to women, whom they fear and distrust, and whose society they shun. They are mostly married but look upon marriage as an infringement on boozing with their pals. They are also... hostile to blacks, college students, welfare recipients, union officials, politicians, women's liberationists. But LeMasters finds that they do not dislike their jobs; on the contrary they voice considerable job satisfaction; as a group they're content with their position in American society and aren't social climbing to move out of the working class."

Working class, labor work, middle class ...etc Whereas there is not distinct line to tell white collar and blue color apart.

There is also the term "pink-collar," which refers to service-industry jobs that are most commonly performed by women, but this term is not as widely accepted, and most "pink-collar" workers are white-collar anyway. No, white-collar work includes any work that isn't manual, thus not being limited to administrative work. Doctors and teachers are professionals, which are a subgroup of white-collar workers.

In the US I haven't really heard any other terms besides "blue-collar" and "white-collar." It basically refers to whether or not your job involves manual labor. It is mostly used in the context of corporations and factories. Yes, teachers are "white-collar workers" but it's not a common way to describe them. To some extent it has to do with the distinction made in the Fair Labor Standards Act of 1938. Workers who are covered by the act punch a time card to record when are working on the job, are often paid by the hour, work a forty-hour work week, may be asked to work more than that but must be paid "time-and-a-half for overtime." These are roughly the same as "blue-collar workers." "Exempt" employees (i.e. except from the act) are typically salaried, work whatever number of hours their supervisor can convince them to work, and (usually) work in a clean office environment and dress more formally than people working on a shop floor. (For example, it is very dangerous to wear a tie if you are working with machine tools!)

I think blue/white collar is more widely used in America but it used in British English. In simple terms Blue collar refers to "factory floor" workers and white collar to those who work in the "office". So, of the two, doctors would be white collar but it does not sound right because they are not really "office" workers.