Varieties of the color blue may differ in hue, chroma, or lightness, or in two or three of these qualities. Variations in value are also called tints and shades, a tint being a blue or other hue mixed with white, a shade being mixed with black. A large selection of these colors is shown below.
Periwinkle flowers
Ultramarine pigment
Bluebonnet flowers
International Klein Blue pigment
Indigo is a term used for a number of hues in the region of blue. The word comes from the ancient dye of the same name. The term "indigo" can refer to the color of the dye, various colors of fabric dyed with indigo dye, a spectral color, one of the seven colors of the rainbow as described by Newton, or a region on the color wheel, and can include various shades of blue, ultramarine, and green-blue. Since the web era, the term has also been used for various purple and violet hues identified as "indigo", based on use of the term "indigo" in HTML web page specifications.
A piece of indigo plant dye from India, about 6 cm (2.5 in) square
Indigo extracted from woad
Newton's observation of prismatic colors: Comparing this to a color image of the visible light spectrum shows that "blue" corresponds to cyan, while "indigo" corresponds to blue.
Indigo bunting