The colors vocabulary defines a protocol for colors, with a concrete implementation for RGBA colors. This vocabulary is used by io.styles, ui and other vocabularies, but it is independent of them.

RGBA colors with floating point components in the range [0,1]:

<rgba> ( red green blue alpha -- rgba )

Converting a color to RGBA:
>rgba ( color -- rgba )

Extracting RGBA components of colors:
>rgba-components ( object -- r g b a )

Further topics:
Color protocol
Standard color database

Color implementations:
CIE 1931 XYZ colors
CIE 1931 xyY colors
CIE 1976 LAB colors
CIE 1976 LUV colors
CMYK colors
Grayscale colors
HSL colors
HSV colors
HWB colors
RYB colors
YIQ colors
YUV colors