Undertones: Underlying pigments that become visible during lightening process

What are Undertones?

Undertones are the subtle, hidden colors that live within your natural hair pigment. They are the secret hues that become visible when you lighten or color your hair, and they play a huge role in how a final hair color looks on you.

Think of your hair’s base color as a canvas. The undertones are the faint background colors painted on that canvas before the main picture goes on top. Most people miss this: your undertone isn’t just one color; it’s often a mix, and it can change over your lifetime.

Why Your Undertones Play Hide and Seek

Your natural hair color is a complex blend of pigments, mainly eumelanin (for brown/black) and pheomelanin (for red/yellow). These pigments aren’t pure. They mix in unique ratios to create your specific shade.

When you apply hair color or lightener, you don’t just add color—you reveal what’s already there. The lightener strips away surface color, exposing those deeper, hidden pigments. This is why two people aiming for the same blonde can get very different results.

I see this constantly in my clinic. A client with dark brown hair might reveal strong red undertones when lightened, while another with the same starting level shows orange or gold. It’s all in their personal pigment recipe.

When Undertones Turn Into Unwanted Brass

Brassiness—those unwanted orange or yellow tones—is simply your natural undertones showing up uninvited. It happens when lightening doesn’t fully neutralize those underlying pigments on the color wheel.

Think of lightening hair like peeling an onion. The first layers you remove reveal warm, golden tones. Go deeper, and you might hit orange, then red. The goal of toning is to cancel these out with opposite colors.

Nearly 80% of my clients who complain of brass misunderstand the cause. They blame the toner or developer, but it’s usually because their underlying pigment wasn’t lifted light enough to be neutralized properly in the first place.

The Undertone Test You Can Do at Home

You can get a clue about your undertones without even lightening your hair. Look at your natural color in direct sunlight. Do you see glints of red, gold, or maybe even ash? That’s your undertone whispering to you.

Another method is the strand test. Snip a few hidden hairs and place them on a pure white piece of paper. Against that background, the secondary colors in your hair become much more apparent.

In my practice, I always analyze hair under a magnifying lamp. This lets me see the pigment distribution clearly. A hair that looks solid brown to the naked eye often reveals a stunning mix of red, gold, and neutral bands under magnification.

Undertones and Your Color Formula

Choosing the right hair color isn’t just about picking a level (lightness/darkness). It’s about selecting a tone that will work *with* your undertones, not fight against them. This is where professional formulation is key.

A colorist uses the underlying pigment as a guide. If your hair reveals gold when lightened, they’ll formulate with a violet-based color to counteract it. If it reveals red, they’ll use green. It’s a precise color correction.

I advise never combining a box dye with a professional color service on the same day. The unpredictable metallic salts and dyes in some box colors can react violently with professional lighteners, causing severe damage in my clinic.

From My Experience

After years of analyzing hair under the microscope, I’ve developed a simple framework I call the “Undertone Hierarchy.” It states that your dominant undertone will express itself in this order of strength: Red/Copper is strongest, then Orange/Gold, then Yellow. Ash is the absence of these warm tones.

This is why it’s so hard to get an ash blonde on naturally dark hair—you have to lift past all those powerful warm stages first. Most at-home failures happen because people don’t respect the strength of their own red or orange underlying pigment.

My proprietary insight is to always assess the client’s skin’s undertones as well. A hair color that perfectly neutralizes the hair’s underlying pigment can still look “off” if it clashes with the warm or cool tones in the client’s complexion. The most harmonious result balances both.

Remember, your undertones are part of your hair’s unique fingerprint. Working with them, not against them, is the secret to color that looks natural, vibrant, and truly “you.”