Treating RGB as a colour space, when the numbers only name a specific colour once a space such as sRGB is attached.
Colour
RGB
Also called red green blue, rgb colour model or rgba. Here is what it means, when it changes what you export, and what people get wrong.
ColourRuns on your deviceUpdated 10 August 2026
The short answer
RGB is the additive colour model screens use, mixing red, green and blue light to produce every colour you see. At 8 bits per channel each of the three values runs from 0 to 255, so 0,0,0 is black and 255,255,255 is pure white.
Updated
The short version
RGB at a glance
| Quick fact | Detail |
|---|---|
| Type | Additive colour model, not a colour space |
| Channels | Red, green, blue, plus optional alpha |
| 8-bit range | 0 to 255 per channel |
| Colours at 8 bits | About 16.7 million |
| Pure white | 255,255,255 (#FFFFFF) |
| Print counterpart | CMYK, which is subtractive |
Slide the table sideways to see every column.
Why does mixing red, green and blue give you white?
RGB is additive. A screen starts black and adds light: drive all three channels to full and the beams combine into white. Ink works the other way round, subtractively, starting from white paper and absorbing light until you approach black, which is why print uses CMYK instead.
Every pixel stores one number per channel. At 8 bits per channel that is 256 steps each, giving about 16.7 million combinations. Add a fourth channel for opacity and you have RGBA, the arrangement PNG and WebP use to carry transparency.
How is RGB different from sRGB?
RGB is a model, not a definition of any particular colour. It tells you there are three channels and roughly what they stand for, but 200, 40, 40 on its own does not say which red. A colour space such as sRGB, Display P3 or Adobe RGB pins that down by fixing exact primaries, a white point and a transfer curve.
The practical consequence is that the same three numbers render as a duller red in sRGB and a more vivid one in Display P3. That is why image files carry a colour profile, and why an untagged file can look wrong when it lands on a wide-gamut screen.
Where does the 255,255,255 rule come from?
Marketplaces that demand a pure white background are asking for exactly that RGB triple. Amazon's product image requirements state that the main image needs a pure white background of RGB 255,255,255, and Walmart Marketplace asks for the same on main images.
A backdrop that photographs as 248, 249, 246 reads as white to your eye and is not white to an automated check. Either light the backdrop until it reaches the top of the range, or replace it outright, then verify with an eyedropper rather than trusting the screen.
What people get wrong about rgb
Each one is a real failure mode, not a style preference.
Assuming a backdrop that samples at 250,250,248 satisfies a pure white requirement, when it does not.
Converting listing photos to CMYK before uploading, which discards colours the screen was perfectly able to show.
Reading a hex code as if it were a different system, when #FF8800 is simply the same RGB triple written in base 16.
Questions people ask
RGB, answered
The follow-up questions people search for once they have the definition.
What do the three numbers in an RGB value mean?
Each number is the intensity of one primary light. In 8-bit images they run 0 to 255, where 0 means that channel is off and 255 means it is at full. So 255,0,0 is full red with no green or blue, and 128,128,128 is a mid grey because all three are equal.
Is RGB better than CMYK?
Neither is better; they describe different physics. RGB adds emitted light and suits screens, CMYK subtracts reflected light and suits ink on paper. Keep photographs in RGB for anything viewed on a device, and convert to CMYK only when a printer asks for it.
What is RGBA?
RGBA is RGB with a fourth channel, alpha, holding opacity per pixel. At 8 bits, 0 means fully transparent and 255 fully opaque. Formats such as PNG, WebP and AVIF store alpha, while baseline JPEG has no alpha channel at all.
Why does the same RGB value look different on my phone and my laptop?
Because the two displays have different primaries, brightness and calibration, and may interpret the file in different colour spaces. Tagging the file with a colour profile and viewing it in colour-managed software narrows the gap, but two uncalibrated screens will never match exactly.
Same cluster
More from the glossary
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Sources
Where the facts on this page come from. Every link opens the specification, standard or documentation the claim was read at.
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