Demi Dye Deep Line
<p>The DEMI Deep Natural Line gathers the brand's <strong>Assalt Arias</strong> permanent hair dye in its deeper shade range, from D-4 through D-9. Each number marks how dark the result lands, while the tone codes after the slash steer the final cast: <strong>WB</strong> for a warm brown, <strong>CB</strong> for a cool brown, and <strong>BB</strong> for a beige brown. That gives a colourist room to dial coverage and undertone separately on the same level.</p><p>These are professional salon dyes from DEMI Cosmetics in Japan, built for grey coverage and for refreshing colour that has shifted over time. The collection sits alongside the rest of our DEMI hair range, so you can match a deep base here with a lighter top note from the wider catalogue.</p>
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Buying guide
DEMI Deep Natural Line: choosing your shade and tone
The Deep Natural Line is the darker end of DEMI's Assalt Arias permanent colour. The naming looks technical at first, but it breaks down into two simple choices: how deep you want to go, and which way you want the brown to lean. This guide walks through both so you can pick with confidence.
What the Assalt Arias Deep Natural Line is
Assalt Arias is DEMI's permanent hair dye system, and the Deep Natural Line is the part of it aimed at richer, darker results. These are oxidative colours, meaning they develop with a separate peroxide developer to lock pigment inside the hair. The line is made for salon use, so the formulas assume some background knowledge of mixing and timing.
Within our catalogue this collection pulls together the D-4 to D-9 shades. Lighter levels of the same range live elsewhere in the DEMI listing, so think of this page as the deep-base shelf.
Reading the D-numbers
The number after the D sets the depth. D-9 is the lightest member of this particular line and D-4 is the darkest, with the in-between numbers stepping down level by level. A higher number lets more light through the finished colour; a lower number reads closer to a near-black brown.
If you are covering grey and want a natural look, pick a depth close to the client's original level rather than going much darker, which can look flat under indoor light.
WB, CB and BB tones explained
The letters after the slash describe undertone. WB is a warm brown that keeps a little gold or red warmth in the result. CB is a cool brown that pulls warmth out and leans ashy. BB is a beige brown, a softer middle ground that mutes obvious warmth without going fully cool.
Two tubes can share the same D-number but finish very differently because of these letters, so the tone code matters as much as the depth.
Matching depth to tone
Because depth and tone are set separately, you can build the exact result you want. A D-7 / WB gives a mid-deep brown with visible warmth, while a D-7 / CB at the same level reads cooler and quieter. The D-5 / BB sits darker with a balanced beige cast that flatters a wide range of skin tones.
When in doubt, choosing a beige brown is the safer route for first-time clients, since it rarely turns brassy or overly cool as it fades.
Covering grey hair
Grey hair resists pigment more than pigmented hair, so deeper levels and longer development time help it take colour. The Deep Natural Line is well suited to this because its richer bases deposit more visible pigment. For stubborn grey around the temples and hairline, apply there first and give it the full processing window.
A warm or beige tone tends to look more lifelike on grey than a strongly cool one, which can read slightly metallic against new growth.
Mixing and developer notes
These dyes need to be combined with an oxidising developer before they will work, and the developer strength changes how much the colour lifts versus simply deposits. For deep deposit-only results, a lower-volume developer keeps the level dark; a higher volume opens the cuticle more and can lighten the natural base slightly.
Always patch test before a full application and follow the timing your developer pairing calls for. Because these are professional products, treat the manufacturer's mixing ratio as the starting point rather than a guess.
Where this collection fits in our DEMI range
This page is the deep-shade slice of a larger DEMI hair colour assortment we carry. If you need a lighter level, a fashion shade, or a toner to finish, browse the wider DEMI listing and pair it with a base from here. Keeping shades from the same brand together makes results more predictable across a full head.
FAQ
Frequently asked questions
FAQ
Frequently asked questions
What does the D-number mean in the Deep Natural Line?
The D-number sets the depth of the shade. In this collection D-9 is the lightest level and D-4 is the darkest, with D-5, D-7 and D-8 stepping between them. A lower number gives a deeper, near-black brown result.
What is the difference between WB, CB and BB tones?
WB is a warm brown that keeps gold or red warmth. CB is a cool brown that leans ashy. BB is a beige brown that softens warmth without going fully cool. Two tubes with the same D-number finish differently depending on this code.
Is the DEMI Deep Natural Line good for covering grey?
Yes. The richer bases in this line deposit more visible pigment, which helps grey hair take colour. Apply to the most resistant areas first, such as the temples and hairline, and allow the full development time.
Do I need a separate developer to use these dyes?
Yes. The Assalt Arias colours are oxidative dyes, so they must be mixed with an oxidising developer before use. The developer volume affects how much the colour deposits versus lifts, so follow the manufacturer's mixing ratio.
Are these professional salon products?
They are. DEMI is a Japanese salon brand, and the Assalt Arias Deep Natural Line is made for professional use. Patch test before any full application and treat the manufacturer's instructions as the baseline for mixing and timing.