Reading a GIA Fancy Colour Diamond Report: Hue, Modifiers and the Nine Grades
By the Byrex Gems team, Toronto · Published 21 October 2026
A GIA fancy colour diamond report describes colour by hue, tone and saturation, names a modifier when one is present, and assigns one of nine grades from Faint to Fancy Deep. Here is how to read each line, with three worked examples and the mistakes buyers make most often.
A GIA Colored Diamond Grading Report describes colour in three parts: a grade term such as Fancy Intense, an optional modifier such as purplish, and the hue, such as pink. The grade term is one of the nine GIA uses: Faint, Very Light, Light, Fancy Light, Fancy, Fancy Dark, Fancy Intense, Fancy Deep and Fancy Vivid. The hue is one of 27 names on GIA's hue circle. The modifier records a second hue that is visible but not dominant, and the last word in the description is always the dominant hue. Read in that order, the colour line says most of what a buyer needs to know.
The rest of the report records the origin of the colour, its distribution, and the usual weight, measurements, clarity and finish. This guide explains each line, reads three report lines as printed, and lists the mistakes buyers of fancy colour diamonds make most often.
What the report contains
Two GIA reports for natural coloured diamonds matter here. The full Colored Diamond Grading Report assesses colour, clarity, polish and symmetry, with a plotted clarity diagram and a proportions graphic. The Colored Diamond Identification and Origin Report is limited to the colour grade and the origin of the colour; GIA offers it for natural coloured diamonds of any size without unstable treatments, and it carries no clarity grade and no plot (GIA's guide to report types).
On the full report the colour section has three lines: Origin, Grade and Distribution, alongside shape, measurements, weight, clarity, polish, symmetry and fluorescence. Many stones carry the report number laser inscribed on the girdle, readable under 10x magnification and listed on the report, so stone and paper can be matched, and any report can be checked against GIA's archive through Report Check.
Hue, tone, saturation and the 27 hues
GIA defines colour with three attributes. Hue is the characteristic colour: red, yellow, green, blue or something between. Tone is the relative lightness or darkness. Saturation is the strength or purity of the colour. The grader judges the overall colour seen from the top of the stone, in a standard viewing box under daylight-balanced light, against master diamonds. The method is set out in GIA's 1994 paper on colour grading of coloured diamonds.
The hue circle carries 27 names built from a handful of base colour words and their combinations: red, orangy red, orange, yellow, green, bluish green, blue-green, greenish blue, blue, purple and purplish red. Pink, brown and grey are not hues in their own right. Pink is GIA's name for red hues at lighter tone and lower saturation, so purplish red becomes purplish pink as the colour weakens; brown and grey are added as modifiers at low saturation, hence brownish pink or grayish blue.
Modifiers: the last word is the dominant hue
When a second hue is visible, GIA names it first; the dominant hue is always the final word. Purplish pink is a pink diamond with a purple component. Pink-purple is a purple diamond with a strong pink component. The suffix "-ish" marks the lighter influence; a hyphenated pair marks two hues closer in strength, with the last still dominant. GIA's 2018 study of pink diamonds defines its sample this way, as stones with pink, purple or red as the final name in the colour description (Gems and Gemology, Winter 2018).
The trade does not price the two alike. A buyer who asks for a Fancy Intense Pink and receives a Fancy Intense Pink-Purple has received a purple diamond. We list pink diamonds and purple diamonds separately for this reason.
The nine grades, and why yellow and brown start at Fancy Light
The first five grades, Faint through Fancy, track tone and saturation together, from barely perceptible to clearly coloured. Above Fancy the terms separate: Fancy Intense is high saturation; Fancy Vivid is the highest saturation at light to medium tone; Fancy Deep is medium to dark tone with moderate to high saturation; Fancy Dark is dark tone without the saturation of Fancy Deep. Each grade covers a range of colour space, so two diamonds of the same grade can differ visibly.
Yellow and brown are the exceptions at the bottom of the scale. GIA's D-to-Z scale already runs from colourless to light yellow, light brown or light grey, and GIA states that a yellow or brown diamond is fancy only when it has more colour than a Z master stone (GIA 4Cs); diamonds with less colour take a letter grade. The first fancy colour grade a yellow or brown diamond can carry is therefore Fancy Light. A blue, pink or green diamond has no place on the D-to-Z scale, so it can be graded Faint, Very Light or Light.
Colour origin, distribution and fluorescence
The Origin line states whether the colour is natural or treated, and reads Natural only when GIA is satisfied that the colour formed in the earth. It matters most for blue and green, two colours that treatment can also produce. Green colour comes from radiation damage, and natural radiation in the ground can leave the same signature as a laboratory, so GIA notes that it is not always possible to separate the two (GIA on green diamonds). When it cannot, the report does not call the colour natural; Rapaport's December 2025 research report describes what a treated or undetermined determination does to a green diamond's price.
The Distribution line reads Even or Uneven. GIA marks it Uneven only when the characteristic colour clearly does not predominate across the stone seen from above, which is uncommon. Fluorescence is reported as for any diamond, from None to Very Strong, with its colour given when present; it is a description, not a grade.
Three report lines, and the mistakes behind them
Fancy Intense Purplish Pink. The hue is pink, with a purple component that is visible but secondary. Fancy Intense is high saturation. Confirm that Origin reads Natural, then watch the stone move, because pink colour is often carried in graining. Had the line read Fancy Intense Pink-Purple, the stone would be purple.
Fancy Light Grayish Blue. Blue is the hue; grey is the low-saturation modifier GIA adds when the blue is muted. Fancy Light is the fourth of nine grades, so this is a light, soft blue rather than the saturated colour of a Fancy Intense or Fancy Vivid Blue. GIA prints American spelling, hence Grayish.
Fancy Vivid Yellow. No modifier, so the hue is a yellow with no visible green, orange or brown component, at the highest saturation grade. For a yellow diamond this is the top of a scale that began at Fancy Light. Canary does not appear on the report; it is a trade name, not a GIA grade.
- Treating trade words as grades. Canary, champagne, cognac and cape are trade names; GIA prints none of them.
- Comparing stones by grade without seeing them. Two Fancy Intense Pinks can differ visibly; every Byrex stone is filmed in our office, unedited, so the colour can be judged first.
- Ignoring the modifier. Fancy Intense Pink, Fancy Intense Purplish Pink and Fancy Intense Brownish Pink are three different stones.
- Skipping the Origin line, or accepting a clarity grade quoted on an Identification and Origin Report, which carries none.
- Not running Report Check or checking the inscription before payment. For how the laboratories differ, see our guide to gemstone laboratories.
Fancy colour diamonds from Byrex Gems
Byrex Gems has served the jewellery trade from Toronto since 1988, and more than seven thousand jewellers, designers and dealers have bought from us. Most of our fancy colour diamonds carry GIA reports, and every stone is filmed in our office, unedited, so what you see is what arrives. Approved trade buyers see prices online. A message on WhatsApp at +1 (437) 450-3786 is answered within hours, and an email to info@byrex.com the same day, seven days a week.
What is listed is a part of what we hold; more is kept in the vault, and what we do not hold we can source through our offices worldwide. Browse our fancy colour diamonds or use Stone Search to filter by colour and intensity. Private viewings are by appointment in Toronto, Hong Kong, Bangkok and Dubai.