You’re standing in the beauty supply aisle, staring at a wall of boxes that all look suspiciously like "just brown." Then you see it. The number 4. It looks safe. It looks dependable. But honestly, most people grab it without realizing it’s the secret weapon of professional colorists. Hair color number 4 isn't just "medium brown." It is the exact midpoint of the hair color scale, the pivot point where cool tones and warm tones fight for dominance, and it’s probably the most mismanaged shade in the entire industry.
It's dark. But it's not that dark. If you’ve ever dyed your hair "dark brown" only to have it look essentially black in photos, you likely made the mistake of grabbing a level 3. Level 4 is where the nuance lives. It’s the color of a double espresso or a well-worn leather jacket. It’s rich.
What Does the Number 4 Actually Mean?
In the Universal Level System used by brands like Redken, Wella, and Matrix, hair is ranked from 1 to 10. Level 1 is the deepest, flattest black. Level 10 is that pale, inside-of-a-banana-peel blonde. Hair color number 4 sits firmly in the "Medium Brown" category.
Don't let the box art fool you. Brands like L'Oréal or Garnier might label their 4 as "Dark Brown," but in the professional world, it’s a medium. This matters because of how light reflects off the hair cuticle. A level 4 has enough pigment to cover stubborn greys completely, yet it’s light enough that you can still see the texture of your waves or curls. When you go darker—to a 3 or a 2—the hair starts to absorb so much light that it looks like a solid, flat helmet. Nobody wants the helmet.
The chemistry here is basically about the underlying pigment. When you lift hair or deposit color at a level 4, you are dealing with a lot of red and red-orange. If you don’t account for those warm undertones, your "chocolate" brown might look a bit like a rusty penny after three washes.
The Difference Between 4, 4N, and 4ASH
This is where people usually mess up their DIY projects. Just because the box says 4 doesn't mean it’s the right 4 for your skin tone. Professional color is coded with letters.
4N (Natural): This is your baseline. It’s balanced. It’s designed to have a neutral reflection. If you have about 50% grey hair, this is your best friend because it has the "brown-to-brown" coverage necessary to hide those wiry silvers.
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4A (Ash): This contains blue or green bases. Use this if you hate warmth. If your hair naturally pulls orange the second a chemical touches it, you need the ash to neutralize that fire.
4W or 4G (Warm/Gold): Think mahogany. Think chestnut. These shades have a "glow" to them. If you have a golden or olive complexion, a flat level 4 might make you look a little washed out, or even tired. Adding that "G" or "W" back in gives the skin a healthy-looking reflection.
I’ve seen so many people try to "fix" a brassy mess by throwing a 4N over it, only to realize the orange is still peeking through like a neon sign. You have to understand the color wheel. If you’re fighting orange, you need blue. It’s physics.
Why Celebrities Love This Specific Level
Ever noticed how stars like Meghan Markle or Priyanka Chopra seem to have hair that looks expensive? It’s rarely jet black. Jet black is harsh. It highlights every fine line on the face. Instead, they often sit right at a hair color number 4.
Why? Because it provides the perfect "canvas" for expensive-looking dimension. You can take a level 4 base and add level 6 "café au lait" balayage highlights. The contrast is high enough to be visible but low enough to look natural. It’s the "old money" aesthetic of hair color.
If you look at the work of celebrity colorists like Tracey Cunningham, she often talks about maintaining the "base" to ensure the highlights don't look "stripey." A level 4 base creates a shadow that makes the lighter pieces pop without looking like a 2002 era chunky highlight disaster.
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The Maintenance Reality Check
Let's be real for a second. Even though it's a "natural" looking shade, a level 4 requires work. Brown hair is notorious for "fading warm." The sun, hot water, and cheap shampoos are all working together to strip the cool molecules out of your hair, leaving you with that muddy, brassy orange.
How to Keep It Rich:
- Cold water only. Okay, maybe not ice cold, but lukewarm. Hot water opens the hair cuticle and lets those expensive 4N molecules slide right down the drain.
- Blue shampoo. You’ve heard of purple shampoo for blondes? Well, for a level 4 brown, you need blue. Blue sits opposite orange on the color wheel. A weekly blue mask will keep your brown looking like dark chocolate rather than a terracotta pot.
- The "Double Wash" Method. Wash once to get the gunk off. Wash again to let the color-protecting ingredients actually do their job.
Dyeing Your Hair at Home vs. The Salon
If you’re going to use a box, please, for the love of all things holy, do a strand test. Hair color number 4 is incredibly pigmented. If your hair is currently a light blonde and you slap a level 4 over it, it might turn muddy or even slightly green. Why? Because blonde hair lacks the "filler" (red and orange) that brown hair needs to look real.
In a salon, a stylist would do a "tint back." They’d basically dye your hair orange or red first to build a foundation, then put the level 4 on top. If you skip that step at home, your hair will look hollow. It’ll look "inky." It won't have that "bounce" that healthy brown hair should have.
On the flip side, if your hair is already dyed a level 2 or 3, a level 4 box dye will do... absolutely nothing. Color cannot lift color. You can't put a lighter brown over a darker brown and expect it to change. You’d need a color remover or bleach first. This is the #1 mistake people make with the number 4. They think it will "lighten" their dark hair. It won't. It will just add more buildup.
The Grey Coverage Secret
One reason hair color number 4 is a top seller globally is its relationship with grey hair. Greys are stubborn. They are coarse. They lack all natural pigment.
A level 5 is sometimes too light to fully "stain" a thick grey hair, leaving it looking like a translucent gold strand. A level 3 can look too "Goth" against aging skin. The number 4 is the "Goldilocks" zone. It has enough ammonia (or ethanolamine in ammonia-free versions) and enough pigment load to drive into the cortex of a grey hair and stay there.
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If you’re DIYing your greys, look for "NN" or "04" on professional labels. These are "double pigment" naturals specifically formulated for hair that refuses to take color.
Is It Right For You?
Choosing a color is about more than just liking the swatch. Look at your wrists. Are your veins blue? You're cool-toned. Go for a 4A. Are they green? You're warm-toned. Go for a 4G. Can't tell? You're probably neutral, and a 4N will look stunning.
Also, consider your eye color. A rich hair color number 4 makes green and blue eyes absolutely electric. The darkness of the hair provides a frame that pushes the lighter iris colors forward. It’s a high-contrast look that doesn't feel as aggressive as black.
Actionable Steps for Your New Look
If you're ready to make the jump to this shade, don't just wing it. Follow these steps to ensure you don't end up with a "hot root" (where your roots are brighter than your ends) or a muddy mess.
- Assess your current level. Use a chart online to see where you are. If you are more than two levels away from a 4, call a pro.
- Buy more than one box. If your hair is past your shoulders, you will run out. Nothing is worse than having half a head of level 4 and half a head of your old "whatever."
- Protect your skin. Use Vaseline or a heavy barrier cream around your hairline. Level 4 pigment stains skin like a permanent marker.
- Process the roots first. Your scalp's heat makes the color develop faster. If you put it on your ends first, they will soak up too much pigment and turn way darker than the rest of your head.
- Gloss it up. Once you've achieved your level 4, use a clear gloss or a "color-depositing" conditioner once a week. Brown hair's biggest enemy is dullness. If it doesn't shine, it doesn't look healthy.
Ultimately, the number 4 is a classic for a reason. It’s the "little black dress" of the hair world. It’s sophisticated, it’s manageable, and when done right, it looks like you were born with perfectly healthy, expensive-looking hair. Stop overlooking the "boring" medium brown—it’s actually the most powerful tool in your beauty arsenal.