Definition of "color-line" []

• In the United States, the social or political line of demarkation between the white or dominant class and persons of pure or mixed African descent. (noun)
• Plural In seal-engraving, and in heraldic work in black and white, fine parallel lines engraved upon the field for the conventional expression of heraldic colors. (noun)
• In psychophysics: The outline of the plane figure (circle, square, triangle) which gives a diagrammatic representation of color sensations and their interrelation. (noun)
• Any straight line joining two points on or within the solid figure (sphere, double cone, double pyramid) which gives a diagrammatic representation of the totality of visual sensations. (noun)

The Century Dictionary (Public Domain)

• "However, she later admitted (Ebony, May 1980) that she really married Hayton to advance her career and cross the “color-line” in show business."
• "If the problem of the 20th century is the problem of the color-line, Du Bois, like the French political theorist Charles Fourier, seemed on the verge of arguing that the greater cause of human misery is due to the primordial theft of property that gave rise to private enterprise and the market economy."
• "Isn't that the very behavior that creates the majority of the color-line problems?"