Prince supports RGB, RGBA, CMYK, and named spot colors. For Prince's color management, please see the Color Management section.
Prince understands CSS basic color names as well as the list of extended color keywords from CSS Color Module Level 4.
To use an RGB color in CSS, it can be expressed either as a value in hexadecimal notation,
as an rgb() function or as a named color. For example, red can be specified
in three ways:
color: #ff0000
color: rgb(255, 0, 0)
color: red
RGBA colors are equivalent to RGB plus an opacity (or alpha) value between 0 and 1.
When the opacity is 0 the color is transparent, and when the opacity is 1 the
color is identical to the RGB color. RGBA colors are expressed as an rgba()
function.
color: rgba(255, 0, 0, 1) // red
color: rgba(255, 0, 0, 0.5) // translucent red
color: rgba(255, 0, 0, 0) // fully transparent
CMYK colors can be specified using the cmyk() or, alternatively, the
equivalent device-cmyk() function syntax. An optional fifth value is
for the alpha channel, i.e. for opacity.
color: cmyk(1, 0, 0, 0) // cyan
color: cmyk(0, 1, 1, 0) // red
color: cmyk(0, 0, 0, 1) // black
color: cmyk(0, 1, 1, 0, 0.1) // translucent red
Prince also supports named spot colors that can be defined with the
@prince-color
rule. An alternate color must also be specified with the alternate-color
property, using any of the valid notations for RGB or CMYK colors. This will be used
in situations where the named color is not available, such as when viewing the generated
PDF file on a display. Please note that alternate-color cannot
be RGBA or CMYKA.
@prince-color MyColor {
alternate-color: rgb(255,0,0)
}
Spot colors can be used with the prince-color() function with a specified
tint value between 0 and 1, which defaults to 1, or alternatively expressed in percentage.
They can also enable overprint:
color: prince-color(MyColor) // tint 1.0
color: prince-color(MyColor, 0.5) // tint 0.5
color: prince-color(MyColor, overprint) // tint 1.0, overprint
color: prince-color(MyColor, 50%, overprint) // tint 50%, overprint
Another way to enable overprint is by using the prince-overprint()
function, which allows to specify a non-transparent color value.