Short answer
Use the system whose purpose matches the job: sRGB (HEX, rgb()) or Display P3 to deliver colours to screens; OKLCH to design palettes, tints and gradients; CIELAB with CIEDE2000 to measure and set tolerances; CMYK only with a named printing condition for print; a spot-colour or standards catalogue such as Pantone or RAL to specify a physical colour to a supplier; and NCS or Munsell to describe and communicate surface appearance. Most real projects use several, converting at the boundaries.
Colour work usually contains four distinct jobs that people try to do with one system. Choosing colours is a design job and wants a space where changes look predictable. Delivering colours is a technical job and wants the format the destination understands. Measuring and approving colours is a quality job and wants an agreed, instrument-supported difference formula. Communicating a physical colour between companies is a contractual job and wants a reference that both sides hold. Picking a system per job — and converting deliberately between them — avoids most of the confusion that arises from using, say, HEX codes to specify paint or CMYK numbers to design a screen palette.
For anything shown on screens, define colours in sRGB for universal delivery and add Display P3 or OKLCH values for wide-gamut screens where they add something. For designing, OKLCH is currently the most practical choice: its lightness predicts contrast-like visual weight across hues far better than HSL, hue stays put when you adjust lightness or chroma, and it is native to CSS. HSL is acceptable for quick picking where accuracy does not matter. Keep a record of the space each token is authored in, because the same numbers in a different space are a different colour.
For approval and quality control of physical colour, CIELAB with CIEDE2000 remains the industrial standard, supported by every instrument; state the illuminant, observer and geometry with every value. For print, work in RGB or Lab and let an ICC profile for the named printing condition generate CMYK; use a spot-colour system when a colour lies outside process CMYK or must match exactly across jobs. For coatings, signage and industrial products in Europe, RAL references are a common contractual language; NCS and Munsell are useful for describing and choosing surface colours by appearance, especially in architecture and interiors.
Every conversion between systems is a decision point. Screen to print needs a profile and a proof. Design OKLCH values to delivery sRGB need a gamut check, with fallbacks chosen by eye where colours fall outside. A catalogue colour to a screen needs an acknowledged approximation. Measured Lab to design tokens needs the reference white converted. Writing down, at each hand-over, which system the value belongs to, what conditions it assumes and what tolerance applies is the single habit that prevents most colour disputes.
| Task | Use | Why | Avoid |
|---|---|---|---|
| Web and app colours for everyone | sRGB (HEX, rgb()) | Universal default; untagged content is sRGB | Unlabelled wide-gamut values |
| Richer colours on capable screens | Display P3 or OKLCH with sRGB fallback | Reaches beyond sRGB; gamut-mapped safely | P3 without a checked fallback |
| Palette ramps, tints, gradients | OKLCH / OKLab | Even lightness steps, stable hue | HSL lightness, RGB averaging |
| Measuring and approving samples | CIELAB with CIEDE2000 | Instrument and industry standard | RGB or HEX distance |
| Commercial print | RGB or Lab master → CMYK via ICC profile | CMYK only means something per condition | Naive CMYK formulas |
| Exact brand ink colour | Spot colour (e.g. Pantone) | Premixed ink beyond process gamut | Assuming CMYK can match |
| Coatings and industrial parts | RAL reference with finish and tolerance | Shared physical standard | Screen swatches as the reference |
| Describing surface colours by appearance | NCS or Munsell | Readable notation, physical atlases | Computing differences in their notation |
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
StandardStrong evidence
CSS defines HEX, rgb() and hsl() as sRGB, and provides oklch(), lab() and color() for other spaces including Display P3.
Source: CSS Color Module Level 4
FactStrong evidence
CIELAB and CIE colour-difference formulas are the CIE's reference methods for colour difference, which is why industrial tolerances are commonly written in them.
ConventionModerate evidence
Using OKLCH for palette design, sRGB/Display P3 for delivery, CIELAB for measurement and profile-driven CMYK for print is a recommended division of labour, not a standard.
Source: CSS Color Module Level 4; International Color Consortium: specifications and information; CIE 015:2018 Colorimetry, 4th edition
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.