Gold by karat and colour, plus platinum, palladium and silver. Every colour here comes from published spectrophotometer measurements, not from a colour picker.
ΔE*ab measures how different two colours look. As a rough guide, around 1 is the smallest difference most people notice side by side. Comparisons across the two measurement studies are approximate.
18K and 14K colours are the ISO 8654 standard colours (nominal values, D65 light, 10° observer). 24K, 22K, 9K, white gold, platinum, palladium, silver and rhodium plating are measured samples from Henderson and Manchanda's study for the Birmingham Assay Office (illuminant C, 2° observer). Colour is defined by measurement, not by recipe: finish, annealing, plating and work-hardening all shift the colour of a finished piece. Tap a card to show it on the left ring.
Why the cards look pale: a flat swatch shows the colour as an instrument measures it, under perfectly even light. Polished gold looks deeper and richer because it mirrors dark and bright surroundings, which is what the rings above show with the same values.
Each shape is the tolerance zone the standard allows around a colour (a* is green to red, b* is blue to yellow); lightness L* has its own range. Enter a spectrophotometer reading of your polished sample, measured with D65 light and a 10° observer, specular included.
A screen can't show these tolerances reliably; a measurement can. Instruments set to a 2° observer read slightly different numbers, which the standard covers in its main tables.
In gold–silver–copper alloys, silver pulls the colour towards green-yellow and copper towards red. Slide between the standard recipes to see the colour move. In-between colours are interpolated from the neighbouring standards, a guide rather than a measurement.
White gold is graded differently
White gold has no N code. It is graded by Yellowness Index (ASTM D1925), the scheme proposed by the British White Gold Task Force and adopted with the MJSA and World Gold Council: the lower the number, the whiter the alloy and the less it relies on rhodium plating.
Each swatch is a real alloy measured in the study (illuminant C, 2° observer, specular included). For comparison, rhodium plating measures 6.8, fine silver 8.4, platinum 10.9 and palladium 13.6 on the same index.
Sources