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What color starts with I in the rainbow?

What color starts with I in the rainbow?

The colors of the rainbow have long fascinated people. From their beauty in nature to their significance in art and culture, the rainbow’s vibrant hues have inspired awe and wonder throughout history. But of the seven main colors most commonly associated with the rainbow, only one begins with the letter “I.” Keep reading to find out what that color is and learn more about the science behind rainbows.

The Colors of the Rainbow

The sequence of colors in a rainbow is often remembered by using the acronym ROY G BIV. This stands for the sequence red, orange, yellow, green, blue, indigo, and violet. Going from the top to bottom of a rainbow, these are the colors that can be seen:

  • Red
  • Orange
  • Yellow
  • Green
  • Blue
  • Indigo
  • Violet

So when considering the question “What color starts with I in the rainbow?”, the answer is clear: indigo!

More About the Color Indigo

Indigo is a deep blue-purple color that sits between blue and violet on the visible spectrum of light. It has a shorter wavelength than blue and violet, meaning it has a higher frequency. The human eye sees indigo as a distinct color when light waves are between about 420-450 nanometers long.

In the 17th century, Isaac Newton first conceived of the visible spectrum having seven distinct colors. He chose to include indigo between blue and violet to match the seven notes of the musical scale. Some scientists argue indigo doesn’t deserve to be considered its own color, since the human eye has difficulty distinguishing it from blue and violet. But indigo remains part of the conventional rainbow sequence.

The deep, rich hue of indigo has intrigued artists and designers for centuries. In various cultures, indigo dye was used to color fabrics, paintings, and other works of art. Denim jeans get their signature blue color from being dyed with indigo. More recently, technology has allowed more consistent recreation of indigo pigments and dyes.

The Science Behind Rainbows

Rainbows are optical phenomena that occur when sunlight interacts with water droplets in the air. Here is a quick overview of how rainbows form:

  • Sunlight shines into water droplets, usually in rain or mist.
  • The sunlight bends (refracts) and reflects off the inside surface of the droplets, splitting into the component colors of the visible light spectrum.
  • The component colors bend or refract at slightly different angles, causing them to spread out into a spectrum or rainbow as they exit the droplet.
  • The rainbow of diffracted light arcs back toward the observer, with red on the outer band and violet on the inner band.

The key factors that must be present to see a rainbow are sunlight, moisture in the air, and an observer in the right position. The sun must be behind the observer, with mist or rain in front of them. The most vivid rainbows form when the sun is lower in the sky, at angles of 40-42° from the observer’s point of view.

More Rainbow Facts

Here are some other interesting facts about rainbows and the color spectrum:

  • Rainbows are optical illusions – they are circular bands of color that appear to arc across the sky, but you can never reach the end of a rainbow.
  • Rainbows follow the observer – the band of colors is always oriented opposite the sun relative to the observer’s perspective.
  • A double rainbow can sometimes form, with a second, fainter arc above the main rainbow.
  • Moonbows and fogbows can also occur at night or in fog, when conditions are right.
  • Each person’s eyes see colors slightly differently – so two people looking at a rainbow may not see the colors at exactly the same positions.
  • There are infinite shades of color visible – the ROYGBIV sequence focuses on the 7 main hues.

The Significance of Rainbows

Beyond their scientific origin, rainbows have long had cultural, religious, and metaphorical significance. Some examples include:

  • In Greek mythology, the goddess Iris created rainbows as she traveled between the lands of gods and men.
  • In the story of Noah’s Ark, God creates a rainbow after the great flood as a sign of his promise and covenant with Noah.
  • Rainbow flags and rainbow symbols are used to represent LGBTQ pride and diversity.
  • Rainbows are used in art and stories as symbols of hope, luck, harmony, dreams, and more.

Rainbows continue to inspire people with their beauty and reflect all the colors that make up the visible light spectrum, including the distinctive hue of indigo.

Reviewing the Question

To summarize, here is a review of the original question:

What color starts with I in the rainbow?

And the answer is:


Indigo sits between blue and violet as the sixth band of color in the sequence red, orange, yellow, green, blue, indigo, violet. Its deep blue-purple hue distinguishes it from the other rainbow colors. While there is some debate over indigo’s status as a distinct color, it remains part of the conventional 7-color rainbow.


The rainbow’s beautiful colors have always captivated people’s imagination. Of the familiar sequence of rainbow colors – red, orange, yellow, green, blue, indigo, violet – indigo is the only one that starts with the letter “I.” Its rich, deep blue-purple hue stands out from the colors around it. The answer to “What color starts with I in the rainbow?” is indigo. Understanding the science behind rainbows helps explain how moisture and sunlight can create this colorful optical phenomenon in the sky.

Data Table

Color Wavelength (nm) Frequency (THz)
Red 620-750 400-484
Orange 590-620 484-508
Yellow 570-590 508-526
Green 495-570 526-606
Blue 450-495 606-668
Indigo 420-450 668-714
Violet 380-420 714-789