SCAA -Agtron: Understanding Roast Levels Through RGB Colors

The Specialty Coffee Association and Agtron: Understanding Roast Levels Through RGB Colors

The Specialty Coffee Association (SCA) created a “Roast Degree” scale to define roast levels precisely. Yet coffee lovers still debate what counts as light, medium, or dark. This article shows a simple, free way to identify your coffee’s roast level using online tools.

A Quick Intro to Agtron

The Specialty Coffee Association (SCAA) — now simply known as the SCA — developed the Agtron number, a color-based standard that helps define roast levels in a measurable way. Instead of vague labels like “light,” “medium,” or “dark,” Agtron provides a numeric system to describe roast color. After all, what looks “light” to one person might look “medium” to another — even between roasters and their customers. So, what exactly is an Agtron number? And what do different Agtron readings mean in terms of bean color and flavor?

Agtron readings are based on the color of either whole roasted beans or ground coffee. Roasters often measure both to better understand how evenly a batch was roasted. As green beans go through the roasting process — from light to medium to dark — their Agtron values decrease. A higher number means a lighter roast, while a lower number indicates a darker one.

The SCAA and the Agtron Color Cards

The SCAA once offered a Roast Color Classification System (product code R400100D), often referred to as the SCAA/Agtron Roast Color Kit. While it is no longer officially sold by the SCA, similar kits — or replicas — can still be found on the market. Prices vary widely, from a few hundred to several thousand New Taiwan dollars, depending on color accuracy and calibration quality. The genuine kits are expensive for a reason: each color chip must be precisely calibrated to avoid color inconsistencies caused by paper, ink, or scanning differences.

Common Agtron Number Ranges

In practice, some ultra-light roasts may show Agtron readings above 100.
Below is a reference to the Roast Color Classification System developed in 1995 by Agtron and the Specialty Coffee Association (SCA).

Differences in Roast Terminology

When you search for Agtron numbers and roast level names online, you’ll find that the definitions vary widely.

For instance, most sources label Agtron 70–60 as Cinnamon Roast, while some instrument manufacturers call Agtron 85 Cinnamon Roast. Others treat Agtron 70 as the start of medium roast. Many roasters even group a wide range of readings under “light roast” — simply to avoid customer complaints about roast color differences.


These inconsistencies stem from differences in instruments, sample handling, or subjective taste perception. It’s not that anyone is “wrong”; roasting itself is inherently relative and subjective.

How Is the Agtron Number Measured?

In simple terms, Agtron readings are based on optical measurements — specifically, how a coffee sample reflects or absorbs light. White light is shone onto the sample, and the reflected light is measured to determine its color intensity. The darker the coffee, the less light it reflects, resulting in a lower Agtron number.

While different instruments or methods may introduce slight deviations, the value of Agtron lies in providing a common, comparable language for the coffee community.
That said, when a roaster lists an Agtron value for a batch, consumers without the same tools can only trust that number — or ask for more details about how it was measured.

Looking at It Through the Lens of Color Science

Six months ago, I was stuck at this stage too. But after learning more about marketing, design, and color theory, I began to understand how different color systems define hues — and how designers use color charts like Pantone to communicate precisely.I hope this article has given you a clearer way to look at roast color — and maybe a new appreciation for the science behind your daily cup.

Fortunately, both academia and industry have already explored this field.
One notable study from the UC Davis Coffee Center, published by the SCA in 2023, proposed the Universal Coffee Color Curve. Using the CIELAB (L*a*b*) color space, the researchers built a color dictionary aiming to make coffee roast color both measurable and communicable.

The team collected thousands of data points from roasting processes — including temperature, time, weight, chemistry, and color — and found that regardless of origin or roast conditions, most samples fell along the same curve in CIELAB space. This finding suggests that CIELAB provides a viable and meaningful way to describe roast color scientifically.


Further Reading
What Color is Your Coffee? | SCA News

A Note on CIELAB and HunterLab

The CIELAB color space, defined in 1976 by the International Commission on Illumination (CIE), uses three parameters:

L* for lightness
a* for the red–green axis
b* for the yellow–blue axis

Practical Applications

In practice, once you have a conversion table, you can use Adobe’s color picker to find an approximate screen color in RGB.
If you need printed materials, you can convert RGB to CMYK and let a professional printer handle color management.

Do note: Adobe’s color picker only accepts integer inputs for L*, a*, and b* values — so the conversion is approximate. For precision down to two decimal places, you’ll need to use mathematical formulas or ask AI tools to perform the conversion.

Final Thoughts

I hope this article gave you a clearer way to look at roast color — and maybe a fresh appreciation for the science behind your daily cup.

Until next time, my friends, and remember:
Do not drift into that good night. ☕

Roast Color Kit and RGB Visual Check Swatch

Important Note on Display Accuracy

Keep in mind that screen colors may vary depending on your device and display settings (such as night mode or blue-light filters).
For best results, use a calibrated monitor or disable any color-altering features when comparing roast colors.

 

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Additional References

SCAA/Agtron Roast Color Kit — no longer officially sold by the SCA.
A source listed by theshop.coffee priced it at AUD 395, about NTD 8,500.
As a chemical engineer at the time, I couldn’t justify spending that much on eight color cards—and now, well, sleeping in the park, I still can’t.
●Agtron Roast Color Kit - SCAA – theshop.coffee




Google search: “scaa agtron roast color card” — you’ll find various images and sources, but few guarantee color accuracy. Prices differ widely depending on reproduction quality.
●Photo source: Google image results for "scaa agtron roast color card" (2025/9/27)

Sensegood Instruments (India) provides a helpful chart comparing Agtron numbers, roast descriptions, and bean appearances.
● Roasted Coffee Color SCAA Agtron Measurement | Sensegood Instruments

Taiwan’s Buon Caffè blog also offers its own Agtron reference chart, complete with locally used roast descriptions. 
●【咖啡知識】各種焙度的咖啡該怎麼挑？就讓烘豆曲線告訴你 - Buon Caffe 步昂咖啡

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