It depends on the color of the shirt you wear to work!
Just kidding. Blue collar implies a person who does manual labor or, pardon the expression, menial tasks such as a secretary. White collar implies professional worker, e.g.. doctors, pharmacists, dentists, insurance agents, etc. Each DI company has their own spin on the occupational classification and different gradations within each classification. You must refer to their manual for the listing of the occupational classifications.
BTW, companies such as Illinois Mutual are usually considered very strong in the Blue/Gray Collar market. Gray collars being those blue collar workers whose shirts were accidentally subject to too much bleach.

Actually, it is those occupations which do not fit neatly into either the blue collar class or the professional class. A secretary may be considered gray collar by some companies.