Achromatic is a word that means “without color.” Across the color spectrum black, white and gray are called “achromatic colors” because they are the only colors that lack hues derived from the primary colors. Black and white are often considered to be the two “true” achromatic colors because they are found in nature and cannot be mixed of already existing colors (just like the primary colors).
Gray is a mixture of black and white so, by default, it is also considered an achromatic color. Yet gray has many differences from black and white. For starters there are several shades of gray that vary wildly from light to dark whereas black and white are generally unchanging. It has also been argued that gray can be considered a form of neutral or earth tone color so it might fit into additional categories, something neither black nor white does.
Achromatic colors, especially black and white, are notable for having the ability to compliment any other color. No color clashes with either white or black—although the same cannot be said for gray. Black and white are also very complimentary toward each other and so the two colors frequently appear together in fashion statements and reoccurring fads. In other words, they are a color combination that never quite goes out of style.
Even though achromatic means without color, the shades included under that term are essential to every color wheel and one’s knowledge of colors!