Plant-based hair colour for grey hair: complete guide for full coverage

Covering grey hair with a plant-based colour is possible — provided you understand why grey resists and apply the right method. This complete guide gives you all the keys to achieving 100% natural coverage, without ammonia or oxidants.

Why grey hair resists plant-based colour

Grey hair has lost its melanin. It is also structurally different: the cuticle is more closed, the fibre smoother and often finer. The pigments from dye plants — indigo, cassia, lawsone — must physically bond to the hair fibre without the help of a chemical oxidant. On melanin-free hair, pigments tend to slide off rather than penetrate.

Three factors amplify resistance:

• Proportion of grey hair: above 50%, results without an adapted method will be translucent.
• Fibre condition: very fine or very smooth hair absorbs pigments less effectively.
• Product residues: silicones and heavy conditioners form an impermeable film. A capillary detox before application is essential.

The 2-step method: the expert solution for guaranteed coverage

Tresse Paris developed the "Base + Colour 2-step method" specifically for hair with a high proportion of grey. The principle: prepare the fibre before applying colour.

Step 1 — Neutral Base

The Tresse Paris Neutral Base (cassia obovata) gently opens the cuticle and deposits a layer of transparent pigments that create a bonding foundation. It does not colour but transforms the surface of grey hair into a receptive fibre.

• Mix: 1 x 100g sachet with water at 70°C
• Processing time: minimum 45 minutes, 1 hour recommended
• Do not shampoo between the two steps

Step 2 — Plant colour

Immediately after (on still-damp hair), apply your plant-based colour. The pigments find a prepared substrate and penetrate evenly.

• Processing time: 1 h to 1 h 30 (extend based on grey density)
• Gentle heat recommended (heating cap or hair dryer over foil)
• Result: uniform coverage, natural tones, lasting 4 to 6 weeks

Strategy based on your proportion of grey hair

The capillary detox: key step before application

Before any plant-based colour — and especially on resistant grey hair — the capillary detox conditions the result. Silicones in many conventional products (masks, conditioners, styling sprays) form an impermeable layer that plant pigments cannot penetrate.

How to perform an effective detox:

• Stop silicone products 2 weeks before: avoid all INCI ingredients ending in "-cone", "-xane" or "-siloxane".
• Clarifying shampoo: 1 to 2 clarifying shampoos (white clay or gentle sulphate-free formula) in the week before application.
• Clean, residue-free, slightly damp hair: never apply on dry hair treated with styling products.

This step accounts for 50% of the result on thick or resistant grey hair. It is often the primary cause of disappointing results when skipped.

Which shade to choose for grey hair?

Not all shades cover equally on grey hair. Darker shades cover better than lighter ones. Our selection optimised for grey hair:

• Espresso: intense chocolate brown, maximum coverage, ideal for all types of grey — the best-seller for predominantly grey hair
• Deep Chestnut: natural chestnut with warm tones, excellent coverage, ideal for chemical → plant transition
• Intense Black: deep black, total coverage with the 2-step method
• Natural Copper: golden copper tones, must be used with Neutral Base for uniformity on grey

Frequency and maintenance after plant-based colour on grey hair

• Recommended frequency: every 4 to 6 weeks, aligned with regrowth speed.
• Between applications: gentle sulphate-free, silicone-free shampoos.
• Cumulative effect: coverage improves with each application. Results are better from the 3rd application onwards.
• No shampoo for 48 h after application: pigments continue bonding for 48 hours. Shampooing immediately weakens the result.

Common mistakes on grey hair

1. Skipping the Neutral Base when grey exceeds 40% — the number one mistake. Without it, colour will be uneven and too light.
2. Water too cool to mix the paste — plant pigments activate at 65–75°C. Below this, the paste is less effective.
3. Processing time too short — 1 hour is the minimum. On resistant grey, 1 h 30 to 2 h gives significantly better results.
4. No heat source — a heating cap or salon dryer hood significantly increases pigment penetration on resistant fibres.

FAQ — Plant-based colour and grey hair

How long does coverage last with the 2-step method?

Between 4 and 6 weeks depending on regrowth speed and care routine. Darker shades last longer.

Can both steps be done on the same day?

Yes, and it is even recommended. Do both applications in the same session. Lightly blow-dry between steps if hair is dripping, but do not shampoo.

Does the 2-step method damage hair?

No. The Neutral Base is 100% plant-based (cassia obovata), with no oxidant. It actually strengthens the hair fibre by providing plant proteins.

What if the result is still translucent?

Increase processing time to 2 hours, use a gentle heat source, and ensure you performed a capillary detox beforehand. Repeat the application one week later if needed.

Does plant-based colour work on 100% grey hair?

Yes, with the 2-step method. 100% grey hair actually responds very well to Neutral Base + Colour because there is no residual melanin to interfere with the tone — the result is pure and uniform.

How many sachets are needed for both steps?

1 sachet of Neutral Base (100g) + 1 to 2 sachets of colour depending on length. For long, thick hair with high grey proportion, plan for 2 colour sachets.

Is plant-based colour safe during pregnancy?

Tresse Paris formulas are COSMOS Organic certified and contain no ammonia, oxidants, or PPD. Consult your doctor as a precaution, but no problematic ingredients are present in our formulas.

→ For more information, see our complete guide to plant-based hair colour or discover our COSMOS Organic certified plant-based colour range.