# What is trichromatic dyeing? Yellow, red and blue explained - URL: https://abdohoo.app/blog/what-is-trichromatic-dyeing - Product: Shadecard (https://sc.abdohoo.app) - Section: Textile & colour - Updated: 2026-09-30 > Trichromatic dyeing builds a shade from three compatible dyes – a yellow, a red and a blue. The ratio sets the hue, the total depth (% owf) sets how dark, and a lab dip confirms. Trichromatic dyeing is the everyday way dye houses build colour: three compatible dyes – a **yellow**, a **red** and a **blue** – are mixed in a chosen **ratio** and applied at a chosen **depth**. The ratio decides the hue; the total amount of dye, written as **% owf** (on weight of fabric), decides how pale or deep that hue comes out. Most commercial shades on cotton, wool, silk, nylon and polyester are made this way, then confirmed and corrected with a lab dip. ## Why three dyes are enough for most shades Dyes work subtractively. Each one absorbs part of the light and lets the rest reflect from the fibre. A yellow dye absorbs blue light, a red absorbs green, a blue absorbs red and orange. Mix them and their absorptions add up: - **Yellow + red** → oranges, rusts, golds and corals. - **Red + blue** → purples, plums, maroons and wines. - **Yellow + blue** → greens, olives and teals. - **All three** → browns, khakis, taupes, greys and near-blacks. With a well-chosen trio, the ratios between them reach most of the colours garments are dyed in. That is why the system is called trichromatic: three colours cover the working range. ## Dial one: the ratio sets the hue A recipe such as **Y 52 · R 43 · B 5** means that of all the dye in the bath, 52 parts are yellow, 43 red and 5 blue. That particular mix is a rust: mostly yellow and red, with a small amount of blue. The small component matters more than its size suggests. Blue is the complement of orange, so a few parts of it **sadden** (dull) the orange towards rust. This is the usual way muted shades are built in a trichromatic system: taupe, sage, mauve and olive are brighter hues with a touch of their opposite added. An olive such as **Y 56 · R 16 · B 28** is a yellow-blue green with red to mute it. Complementary pairs to keep in mind: ColourIts complement (saddens it)OrangeBlueGreenRedVioletYellow![Shadecard library search for olive: Dark Olive Y 52 R 18 B 30 deep, and Olive Y 56 R 16 B 28 medium, each with a yellow-red-blue ratio bar](https://abdohoo.app/media/library/shadecard/android-library-search.webp)Two olives in the Shadecard library: similar ratios, different depths## Dial two: depth sets how dark The same ratio can give a pastel or a deep shade. What changes is the total dye as a percentage of the fabric weight: Depth bandTypical total dyePastel0.1–0.5% owfLight0.5–1% owfMedium1–2% owfDark2–4% owfVery dark4–8% owf and moreThese are indicative ranges. A dye with high colour strength reaches a given depth with less; fibres and dye classes differ; and above roughly 4–6% owf many baths stop exhausting efficiently, which is one reason true blacks are usually a dedicated black dye rather than a very deep trichromat. ## From ratio and depth to grams The arithmetic is simple: **dye (g) = fabric weight (g) × % owf ÷ 100**, then split by the ratio. For 200 g of cotton at 2% owf, the total is 4 g of dye. With the rust ratio above: - Yellow: 4 × 0.52 = **2.08 g** - Red: 4 × 0.43 = **1.72 g** - Blue: 4 × 0.05 = **0.20 g** ![Shadecard recipe calculator result: Yellow 2.08 g, Red 1.72 g, Blue 0.20 g, bath 2.0 L, salt 100 g, soda ash 30 g](https://abdohoo.app/media/library/shadecard/android-calc.webp)The same sum in Shadecard's recipe calculator (200 g, 2% owf, water ratio 1:10)Weighing 0.20 g accurately is hard, which is why labs dissolve dyes as stock solutions and pipette them. See [How to make and use a dye stock solution](https://abdohoo.app/blog/how-to-make-dye-stock-solution). ## Why the three dyes must be compatible Three dyes in one bath must behave like one. If the yellow rushes onto the fibre in the first ten minutes while the blue arrives slowly, the hue changes during dyeing and any change in time or temperature shifts the final shade. Dyers match their trichromat on: - **Exhaustion profile** – similar time and temperature curves onto the fibre. - **Affinity** – similar preference for fibre over bath, so no dye dominates early. - **Migration and levelling** – similar ability to even out. - **Sensitivity** – similar response to temperature, salt, pH and liquor ratio. - **Fastness** – similar wash and light fastness, so the shade does not change hue as it fades. Dye makers sell trichromatic sets that are matched this way for each dye class. A useful rule: use the fewest dyes that reach the shade. ## The ratios travel; the chemistry doesn't The idea of a Y:R:B ratio works on any fibre, but the dyes do not. The fibre decides the dye class: FibreDye classCotton, viscose, linenReactive (also direct, vat)Wool, silkAcid, metal-complexNylonAcid (also disperse)PolyesterDisperse, at high temperatureAcrylicBasic (cationic)BlendsTwo classes, one or two bathsA ratio that works with one set of reactive dyes is a starting point with another set, not a copy. ## Where trichromatic dyeing runs out - **Brilliant turquoise and green** are beyond a standard blue's reach and usually need a turquoise dye. - **Black and navy** are demanding: black is often a dedicated dye, and navy can drift red or green between lots. - **Greys, beiges and pastels** use very little dye, so small weighing errors are large relative errors. - **Fluorescent colours** emit light and cannot be built from ordinary dyes. ## A short glossary - **Hue** – which colour family: red, orange, olive, teal. Set by the ratio. - **Depth** – how much dye relative to the fabric, in % owf. Sets how pale or deep. - **Chroma** – how vivid or greyed the colour is. Lowered by the complement. - **Saddening** – adding a little of the complementary dye to mute a colour. - **Tint, shade, tone** – paler (less dye), deeper (more dye), duller (complement added). In a dye house "shade" often just means the colour itself. - **Trichromat** – the three compatible dyes used together. - **Exhaustion** – how much of the dye leaves the bath for the fibre. - **Lab dip** – the small trial dyeing that confirms a recipe. ## Getting to the first recipe faster The hardest part is often the first guess: looking at a customer's swatch and writing a ratio. Shadecard measures the swatch with a phone camera and a sheet of white paper, finds the nearest of 13,297 library shades, and gives its Y:R:B ratio and a depth estimated from the fabric's own lightness. The app is explicit that this is a starting point: every recipe ends with *confirm with a lab dip*. See [Understanding the trichromatic recipe](https://abdohoo.app/help/shadecard/trichromatic-recipe-explained) and [Use the recipe calculator](https://abdohoo.app/help/shadecard/recipe-calculator). However you arrive at the first ratio, the trichromatic method always finishes the same way: dye a small swatch, compare it with the target, correct, and only then dye bulk. More in [The lab dip process explained](https://abdohoo.app/blog/lab-dip-process-explained). ## Frequently asked questions ### What are the three primary dyes in trichromatic dyeing? A yellow, a red and a blue from the same dye class, chosen as a compatible set. In practice the red is often a bluish red and the blue a bright blue, so that together they reach the widest range of shades. ### What does % owf mean? On weight of fabric: the total dye as a percentage of the dry fabric weight. 2% owf on 1 kg of cotton means 20 g of dye in total, split by the ratio. ### Can every colour be made from three dyes? Most practical shades, but not all. Brilliant turquoises and greens often need a dedicated turquoise dye, true blacks usually use a dedicated black, and fluorescent colours cannot be built at all. ### Why do the three dyes need to be compatible? If they move onto the fibre at different speeds or react differently to temperature, salt or pH, the hue drifts during dyeing and from batch to batch. ### Is a trichromatic recipe from an app ready for bulk? No. It is a starting point. Confirm and correct it with a lab dip on your own fabric, dyes and process before dyeing bulk.