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Is indigo the same as purple?

Is indigo the same as purple?

Indigo and purple are often used interchangeably, but they are actually two distinct colors with some key differences. While they look similar to the naked eye, when examined more closely there are clear variations in their hue, shade, and frequency on the light spectrum. Understanding the nuances between indigo and purple requires an in-depth look into color theory, light waves, and the history of dyes and pigments. By exploring all facets of these colors, we can better appreciate their unique characteristics.

Defining the Colors

Indigo and purple fall next to each other on the visible spectrum of light. Sir Isaac Newton first identified indigo as a distinct color in the 1660s when he developed the first color wheel. Newton placed seven colors along the visible light spectrum: red, orange, yellow, green, blue, indigo, and violet. He chose these hues because the human eye can detect that each one has its own unique wavelength and frequency.

Later scholars condensed Newton’s color wheel into the six main rainbow colors by eliminating indigo. They determined that the difference between violet and indigo is so subtle that the human eye has difficulty distinguishing between them. Most modern color wheels use the ROYGBV scheme. However, indigo dye has still remained its own distinctive shade.

On the modern color spectrum, purple is a secondary color made by combining the primary colors red and blue. Purple sits between violet and magenta. Indigo, by contrast, is a tertiary made by mixing the primary color blue with the secondary color purple. As a result, indigo is a darker, more saturated version of purple.

Hue Differences

The most noticeable difference between purple and indigo is hue, which essentially refers to the dominant wavelength or color.

Purple has a hue ranging from red-violet to blue-violet. It sits between magenta and violet on the color wheel. This gives purple tones of both red and blue. Lavender, lilac, and plum are examples of shades of light purple, while eggplant and amethyst have much darker purple hues.

Indigo has a stronger blue hue compared to purple. More specifically, indigo ranges from blue to blue-violet. Unlike purple, indigo does not contain traces of red. This gives indigo a deeper, rich bluish-purple tone. While purple takes on redder or pinker hues, indigo stays solidly cool and blue-based.

Color Shade Variations

Indigo and purple also differ in shade, which refers to how light or dark a color is. Purple is available in a vast range of light, medium, and dark shades. Light purples include lavender, lilac, mauve, and wisteria. Medium shades include periwinkle and orchid. Darker purples include eggplant, boysenberry, and purple heart. The flexibility of purple shades makes it easy to find lighter or darker variations.

Since indigo sits next to violet on the color wheel, it has a much darker, richer shade. Indigo tends to be very close to black, lacking the lightness and brightness of many purple hues. At the same time, indigo is less intense than the deepest eggplant purple shades. Instead, it has a very deep midnight blue tone.

Differences in Pigments and Dyes

Throughout history, purple and indigo have come from different pigments and dyes. Purple originally came from the secretion of a Mediterranean mollusk known as Tyrian purple. It created a reddish-purple pigment that was highly coveted and valued. Later, a synthetic version of this purple was derived from coal. On the other hand, indigo dye originally came from the leaves of Indigofera plant species native to Asia and Africa. Indigo dye was cheaper than rare Tyrian purple, allowing it to become popular for dyeing fabrics.

In more modern times, purple and indigo pigments and dyes have been synthesized in labs. Indigo dye remains distinct from purple dyes. Pigment chemists can even select the particular chemical composition that yields indigo’s signature hue.

Distinction in Optics

Optics research shows that indigo and purple bend light waves differently. Sir Isaac Newton originally showed this when he used prisms to separate sunlight into the visible color spectrum. The indigo wavelength measures around 445-420 nm, while violet and purple measure around 380-450 nm. This research proved that indigo bends light to a measurably different degree than purple.

Modern scientists have delved even further into the optical distinctions between indigo and purple. New LED lighting technology can emit narrow bandwidths of light. By tuning LED lights to indigo’s exact wavelength, they emit the same hue seen in a rainbow. This shows that indigo has unique optical properties not fully reproducible by mixing blue and purple light.

Uses Across Cultures

Indigo and purple have carried important but distinct cultural meanings across civilizations. In Asia, indigo dye was precious and prized. Japanese indigo dye masters helped popularize the color through the art of shibori dying. Indigo’s deep blue tone inspired philosophers to associate it with depth of thought and intuition. Buddhist monks wore indigo robes to represent wisdom and discipline.

In the West, purple took on more royal connotations. Because Tyrian purple dye was so rare and laborious to produce, it became associated with prestige. Roman emperors and European kings wore purple robes and decorated with purple tapestries. The rarity of purple fabrics held important social symbolism.

So while both colors carry cultural significance, indigo was known more for its artistry and spirituality in the East. Purple held more royal and wealthy associations in Europe.

Gender Associations

Indigo and purple also differ in their gender connotations. Throughout the 20th century, purple became strongly associated with females. The soft, light shades became a hallmark of women’s fashion and decoration. Indigo, on the other hand, maintained a more gender-neutral status. Its darker hue reads as masculine or feminine depending on the context.

Recent decades have seen the gender norms around colors become more flexible. However, indigo is still likely to code as more gender-neutral than the traditionally feminine hues of purple. Purple remains strongly associated with the delicate and romantic.

A Matter of Taste

When it comes down to it, indigo versus purple is largely a matter of individual taste and aesthetics. Designers, artists, and decorators choose between the two hues based on their needs. Purple has an advantage in the vast number of light and dark shades it offers. Indigo’s narrower spectrum gives it a particular bold look. Those drawn to a rich, inky tone may favor indigo over purple’s more feminine air. Overall, the context dictates whether indigo or purple better suits the mood.

Similarities Between the Colors

Although they have distinct differences, indigo and purple do share some key similarities:

  • They are both tertiary colors that combine blue as one of their primary hues.
  • They sit next to each other on the color wheel between violet and blue.
  • They both have a cool, rather than warm, color temperature.
  • Richer shades of indigo and purple were historically prized as dyes.
  • They both can symbolize wealth, power, spirituality, or mystery depending on culture.
  • They function as analogous colors that create a monochromatic color scheme.

So while indigo and purple have unique variations in hue, shade, dye composition, and connotations, they share more similarities than differences. They ultimately blend together as tones of rich blue-violet.

Key Differences Between Indigo and Purple

To summarize, here are the major differences between indigo and purple:

Indigo Purple
Has hue ranging from blue to blue-violet Has hue ranging from red-violet to blue-violet
No traces of red Contains traces of red
Very dark, close to black Available in pale to very dark shades
Originally came from indigofera plant dyes Originally came from Tyrian sea snail pigment
Measures 420-445 nm wavelength of light Measures 380-450 nm wavelength
Gender neutral associations Traditionally feminine associations


Indigo and purple are incredibly close on the visible color spectrum. But despite the similarities, they have distinct differences in terms of hue, shade, cultural meaning, and gender connotations. Indigo maintains a richer blue that separates it from the red tones of purple. When examining the nuances of color, indigo and purple should be considered unique but complementary colors. They offer artists, designers, and anyone who loves color two lush options to work with.