What Does RGB Stand For?

What does RGB stand for, and why those three colors?

Red, green and blue are the primary colors of light. The human eye has three types of color sensing cells, and they respond most to long, medium and short wavelengths, which line up roughly with red, green and blue. By controlling just those three, a screen can trick the eye into seeing yellow, purple, orange and millions of other colors.

This is called an additive model. Adding more light makes the color brighter:

• Red plus green light makes yellow.
• Green plus blue makes cyan.
• Red plus blue makes magenta.
• All three at full strength make white.
• None of them makes black.

Reading RGB values and hex codes

Each channel gets a number. In standard 8 bit color, the range runs from 0 (off) to 255 (full brightness). That gives 256 levels per channel and 16,777,216 possible colors in total.

A hex code is the same three numbers written in base 16, two digits per channel. Web designers type these into CSS to color text and backgrounds on HTML pages.

RGB vs CMYK

Printers work the other way. Ink absorbs light instead of giving it off, so print uses a subtractive model called CMYK: cyan, magenta, yellow and key (black). Mixing more ink makes the result darker.

• Use RGB for anything seen on a screen: websites, apps, videos, slides shown on a projector, social posts.
• Use CMYK for anything printed: flyers, business cards, packaging, posters.

Bright RGB colors, like a glowing neon green, often look duller in print because ink cannot match them. Designers check a CMYK proof before sending a file to a print shop. Image formats such as PNG store RGB color and are meant for screens.

RGB lighting on computer gear

When a keyboard, mouse, fan or desk lamp is sold as RGB, it means each light contains red, green and blue LEDs that can blend into many colors. Software lets you pick a steady color, a slow fade or a wave that runs across the keys. Some setups sync lights across several devices.

A related term is ARGB, addressable RGB, where each LED can show a different color at the same time. Plain RGB strips usually change all lights to one color at once.

How to say and write RGB

Out loud, it is "ar jee bee." On the page, keep all capitals and drop any dots. The "ar" sound takes an, so you write an RGB monitor or an RGB value. The order is always red, green, blue, so 255, 0, 0 is red, never blue.

You may also see RGBA, which adds an alpha channel for transparency, and sRGB, the standard color space most screens and web pages assume. For more screen and file terms, see the tech acronyms section.

RGB in example sentences

• "Export the logo file in RGB for the website and CMYK for the printer."
• "Set the background to RGB 240, 240, 240 for a soft gray."
• "His keyboard has RGB backlighting that pulses with the music."
• "Each pixel on the screen is made of red, green and blue subpixels."