You’ve seen it a thousand times. That glowing arc stretching across the highway after a summer storm. Your brain probably defaults to the old "ROYGBIV" acronym you learned in second grade. But if you actually stop and look—really look—you’ll notice that red is always sitting right there at the top. It’s the outer edge. The leader of the pack.
Red is the first colour of rainbow.
It isn't a random choice by nature. It isn't because red is "bold" or "aggressive" in some poetic sense. It’s physics. Pure, unadulterated science involving water droplets and light waves. When you see that crimson band, you're actually seeing the result of light being bent at a very specific, very stubborn angle.
The Physics Behind Why Red Takes the Lead
To understand why red is the first colour of rainbow, you have to think about how light travels. Sunlight looks white, but it's a messy cocktail of every color imaginable. When that light hits a raindrop, it slows down. It bends. Scientists call this refraction.
Think of it like a car hitting a patch of sand. If you hit the sand at an angle, the car slows down and turns. Different colors of light "turn" at different rates. Red light has the longest wavelength in the visible spectrum. Because its waves are long and lazy, it doesn't get pushed around as easily as the others.
While violet light (at the bottom) has short, choppy waves that scatter and bend aggressively, red light is the tank of the color world. It resists bending. According to the National Center for Atmospheric Research, red light exits the water droplet at an angle of approximately 42 degrees.
Because it bends the least, it stays at the top of the curve from your perspective on the ground.
💡 You might also like: Why Every Mom and Daughter Photo You Take Actually Matters
Does the Order Ever Change?
Honestly, no. Not in a primary rainbow.
If you see a double rainbow, things get weird. The secondary bow—that fainter one hovering above the main event—actually has the colors reversed. In that case, violet is on the outside and red is on the inside. This happens because the light reflects twice inside the water droplet before coming out. It’s like a mirror of a mirror.
But for the standard, bright rainbow we all know and love? Red is always the pioneer.
Isaac Newton and the Seven-Color Myth
We can't talk about the first colour of rainbow without mentioning Sir Isaac Newton. Back in the 1660s, he was messing around with prisms in a dark room. He was the one who realized that white light wasn't "pure" but was actually made of different colors.
Interestingly, Newton originally only saw five colors: red, yellow, green, blue, and violet.
He eventually added orange and indigo. Why? Not because he suddenly saw them better, but because he had a thing for the number seven. He believed the universe was built on mathematical harmonies, similar to the seven notes in a musical scale or the seven known planets at the time.
📖 Related: Sport watch water resist explained: why 50 meters doesn't mean you can dive
So, while we say red is the first of seven, the "seven" part is actually a bit of a human invention. In reality, a rainbow is a continuous gradient. There are millions of shades in there. There is no sharp line where red ends and orange begins. It's a smear of light. We just like to put things in boxes.
Why Red Matters More Than You Think
Red isn't just the first colour of rainbow in a physical sense; it’s also the first one we "see" culturally.
Linguists like Brent Berlin and Paul Kay conducted a famous study in 1969 regarding how languages develop names for colors. They found a fascinating pattern. If a language only has two color words, they are always "black" and "white" (or light and dark). If they have a third word? It is almost always red.
It’s the most primal color. It’s the color of blood, fire, and ripe fruit. It grabs our attention faster than any other hue. This is probably why your eyes naturally gravitate to that top band of the rainbow first. It’s literally hard-wired into our biology to notice red.
Light, Atmosphere, and the "First" Sensation
There’s also the matter of what happens during sunset. Have you ever noticed that a rainbow near dusk looks almost entirely red?
This is because the sun’s light has to travel through much more of the Earth’s atmosphere when it’s low on the horizon. The shorter wavelengths (blue and violet) get scattered away by all the nitrogen and oxygen molecules. Only the long, sturdy red waves make it through the gauntlet.
👉 See also: Pink White Nail Studio Secrets and Why Your Manicure Isn't Lasting
In these moments, red isn't just the first color; sometimes it’s the only color.
Common Misconceptions About Rainbows
People often think rainbows are "objects" sitting in the sky at a specific location. They aren't. A rainbow is an optical phenomenon that exists only in the relationship between the sun, the water, and your eyes.
- You can't reach the end: Since the rainbow moves as you move, you'll never find the pot of gold.
- They are actually circles: If you were in an airplane, you wouldn't see an arc. You'd see a full circle of color. Red would be the outermost ring of that circle.
- Everyone sees a different rainbow: Because your eyes are in a different spot than mine, the light hitting your pupils is coming from different droplets. My "red" is slightly different from your "red."
How to Capture the First Color Perfectly
If you're into photography, capturing the first colour of rainbow requires more than just pointing and clicking. To make that red pop, you need to understand contrast.
- Use a Polarizing Filter: This is a game-changer. It cuts down on the glare from the water droplets and makes the colors—especially the red—look way more saturated.
- Under-expose slightly: If your camera tries to make the image too bright, the red band will look washed out or orange. Knock the exposure down a notch.
- Find a dark background: A rainbow against a dark, stormy gray sky will always look more dramatic than one against a light blue sky.
The red band is the most frequent victim of "bleed" in digital photos. If you look closely at a cheap smartphone photo of a rainbow, the red often looks like a blurry mess. This is because red light has the lowest frequency and sometimes the sensor's pixels can't define the edge properly against a bright sky.
Practical Steps for Rainbow Spotting
You don't have to wait for luck. You can predict when the first colour of rainbow will appear if you know the formula.
First, the sun must be behind you. Always. If you are looking at the sun, you won't see a rainbow.
Second, the sun needs to be relatively low. If the sun is higher than 42 degrees in the sky, the rainbow is actually below the horizon where you can't see it. This is why you mostly see rainbows in the late afternoon or early morning.
To see the most vivid red band possible, wait for those "sun-showers" where the rain is heavy but the sun is peeking through a gap in the clouds. The larger the raindrops, the more brilliant the colors. Small mist produces pale, white-ish rainbows (often called fogbows). Big, fat summer raindrops produce a red so deep it looks like it was painted on the sky.
Next time you see a storm clearing, turn your back to the sun and look for that 42-degree angle. Look for that leading edge of crimson. It's the longest wave, the least-bent light, and the first chapter in the story of how our atmosphere talks to the sun.