You’re standing in the drugstore aisle. It’s brightly lit, slightly clinical, and you’re staring at a wall of smiling models with perfect hair. You pick up a box because the girl on the front has that exact Pinterest-board mushroom blonde you’ve been dreaming about. You go home, slap it on, wash it off, and suddenly you’re looking at a patchy, muddy orange mess in the mirror. It’s heartbreaking. But honestly, it’s not your fault—it’s the fact that you were looking at the picture instead of the hair dye colour chart numbers.
Those tiny digits on the top of the box aren't just inventory codes for the warehouse. They are a universal language used by professional colorists from London to Tokyo. If you don't speak the language, you're basically gambling with your cuticles.
Deciphering the International Colour Code
Most people think a "Level 7" is just "blonde." It’s not. In the professional world, the first number in that sequence tells you exactly how light or dark the hair is on a scale of 1 to 10. 1 is the deepest, flattest black you can imagine. 10 is a pale, Nordic blonde that almost looks like inside of a banana peel.
Some brands like L'Oréal or Wella might even sneak in an 11 or 12 for "high lift" shades, but for most of us, the 1-10 scale is the Bible. If your natural hair is a Level 4 (medium brown) and you buy a box that starts with a 9, you are going to have a bad time. Why? Because hair dye isn't magic ink. It's chemistry. Without a high-volume developer or bleach, a Level 9 dye isn't going to show up on Level 4 hair. You’ll just end up with "hot roots" and a lot of regret.
The Point, Slash, or Dash: What Comes After the Level
This is where things get spicy. The number after the dot—like the .3 in a 7.3—is the "tone." While the first number tells you the depth, the second number tells you the "flavor." Is it warm? Is it cool? Is it going to turn your hair the color of a copper penny or a sheet of slate?
Usually, the breakdown looks something like this across major brands:
🔗 Read more: Finding the Perfect Pic of Forget Me Nots: Why These Tiny Blue Flowers Are Harder to Shoot Than You Think
- .0 is Neutral (Natural)
- .1 is Ash (Blue/Green base)
- .2 is Iridescent/Violet
- .3 is Gold
- .4 is Copper
- .5 is Mahogany
- .6 is Red
- .7 is Tobacco/Matte (sometimes Green)
If you see two numbers after the dot, like an 8.13, the first one is the "primary" tone and the second is the "secondary" tone. In an 8.13, you’ve got a light blonde that is mostly ash but has a tiny hint of gold to keep it from looking like a sidewalk. It’s a delicate balance. Professionals spend years learning how these pigments cancel each other out. It's called color theory, and it's why your stylist gets paid the big bucks.
Why Your "Ash" Turn Out Green (The Undertone Trap)
Let’s get real about the color wheel. If you have dark hair and you try to go lighter, your hair naturally reveals "warmth." Think of it like stripping paint off an old house. Underneath that brown is red. Under the red is orange. Under the orange is yellow.
If you use a .1 (Ash) dye on hair that has a lot of yellow undertone, what happens? Simple primary school art: Blue + Yellow = Green. You’ve just accidentally turned yourself into a swamp creature because you didn't account for the underlying pigment. This is the biggest mistake DIYers make with hair dye colour chart numbers. They pick the "goal" color without looking at the "starting" color.
Expert colorists like Josh Wood often talk about "neutralizing" rather than just "coloring." If you have too much orange, you need a blue-based tone. If you have too much yellow, you need violet. If you look at a professional chart and see a 9.2, that's a very light blonde with violet tones—perfect for killing that "chunky butter" look after bleaching.
The Secret of the Double Zero
Ever seen a 6.00 or a 5.0? That extra zero isn't a typo. It usually signifies "Intense" or "Deep" pigment, specifically designed for stubborn grey hair. Grey hair is a different beast entirely. It’s coarse, it’s lost its natural pigment, and it’s "unpigmented," meaning it resists holding onto color.
If you have 100% grey coverage needs, a standard 7.3 might just leave your greys looking like translucent yellow wires. You need that .0 or .00 to provide the "meat" of the color so the tone has something to grab onto.
✨ Don't miss: Bearded Iris Sylvan Supply: Why This Specific Cultivar is Taking Over Southern Gardens
Letters vs. Numbers: The American Confusion
Just to make things harder, some brands (especially in the US like Matrix or Redken) use letters instead of numbers for the tones. It’s the same logic, just a different alphabet.
- A = Ash
- G = Gold
- C = Copper
- V = Violet
- N = Neutral
So, a 6.1 in European numbering is a 6A in American letter-coding. Both mean "Dark Ash Blonde." Don't let the branding fool you; the chemistry inside the tube is remarkably similar. If you're switching brands, always check if they follow the numerical or alphabetical system before you mix that developer.
How to Actually Use This at Home
Stop looking at the girl on the box. Seriously. Turn the box over and look at the "Before and After" chart, but even that is often a lie. Instead, find your current level. Be honest. If your hair is dark, you’re a 3 or 4.
- Identify your starting level. Hold a strand of hair up to the light. If it's dark brown but not black, you're a 4.
- Decide your goal level. You can usually only go two levels lighter or darker with "box" dye without it getting weird. If you're a 4, don't try for anything higher than a 6.
- Pick your tone. If you hate "warmth," look for a .1 or a .2. If you want to look like a sunset, go for .4 or .6.
Real-World Nuance: The Developer Factor
The box doesn't tell you what "volume" of developer is inside. Usually, it's 20-volume. This provides about two levels of lift. If you buy a Level 10 dye but you have Level 5 hair, the 20-volume developer isn't strong enough to get you to that 10. You’ll end up with a muddy Level 7 orange.
Professional stylists like Guy Tang or Brad Mondo have built entire careers on explaining this "lift and deposit" relationship. You can't just put "light" on "dark" and expect it to work like a crayon on white paper. It's more like putting a blue filter over a red lightbulb.
Practical Steps for Your Next Colour Session
Before you touch your hair, do a "strand test." I know, it’s boring. No one wants to wait 30 minutes with a tiny snippet of hair in a bowl. But it's better than wearing a beanie for three months.
- Check the lighting: Only judge your hair color in natural daylight. Bathroom LEDs are liars. They can make an ash tone look green or a gold tone look orange.
- Porosity matters: If your ends are dry and frizzy, they will soak up the "tone" like a sponge. This is why some people end up with brown hair but blue ends. Apply your color to the roots first, and only pull it through the ends for the last 5-10 minutes.
- The "Safety" Rule: When in doubt, always go one shade lighter than you think you want. It is much easier for a professional to fix hair that is too light than it is to scrub out dye that turned out "accidental goth" black.
Don't Forget the pH
Hair dye is alkaline; it opens the hair cuticle. Once you're done, you need to close that cuticle back up. Use a pH-balanced conditioner (usually included in the box). If the cuticle stays open, your expensive new color will literally just wash down the drain the next time you shower.
Investing in a sulfate-free shampoo is also non-negotiable. Sulfates are basically dish soap for your head—they'll strip a Level 5.5 Mahogany down to a dull brown in three washes. Use cold water if you can stand it; it keeps the hair shaft sealed and the color locked in.
Understanding hair dye colour chart numbers turns a stressful DIY project into a predictable science experiment. You aren't just "dyeing your hair" anymore; you're formulating. And that's the difference between a "box job" and a look that has people asking which salon you went to.
Actionable Next Steps
- Audit your current hair: Use a professional level finder (searchable online) to determine if you are truly a 4, 5, or 6.
- Check your skin undertone: If your veins are blue, you're cool-toned—stick to .1, .2, or .7. If they're green, you're warm—look for .3, .4, or .5.
- Buy a bowl and brush: Stop using the "squeeze bottle" that comes in the box. Applying with a brush allows you to saturate the hair evenly, which prevents the dreaded "patchy" look.
- Map your history: If you have old dye on your ends, a new "lighter" dye will not lift it. Color cannot lift color. If you're going lighter over old dye, you need a color remover first.