RGB

1Initialism of red, green, blue; an additive color model in which colors are represented by adding varying amounts of red, green, and blue light.
2loosely, attributivelySomething extending across the RGB color space; (especially) something having a wide variety of vivid colors.
3by extension, slangRGB lighting; lights (especially LEDs) able to display a wide range of colors by being able to individually adjust the strength of the red, green, and blue channels.
4(astronomy) Initialism of red-giant branch. A classification of stars.