this version will run with npm start, but when attempting to run the built version behind nginx, it appears to have issues
PostCSS Color Functional Notation 
PostCSS Color Functional Notation lets you use space and slash separated color notation in CSS, following the CSS Color specification.
:root {
--firebrick: rgb(178 34 34);
--firebrick-a50: rgb(70% 13.5% 13.5% / 50%);
--firebrick-hsl: hsla(0 68% 42%);
--firebrick-hsl-a50: hsl(0 68% 42% / 50%);
}
/* becomes */
:root {
--firebrick: rgb(178, 34, 34);
--firebrick-a50: rgba(178, 34, 34, .5);
--firebrick-hsl: hsl(0, 68%, 42%);
--firebrick-hsl-a50: hsla(0, 68%, 42%, .5);
}
Usage
Add PostCSS Color Functional Notation to your project:
npm install postcss-color-functional-notation --save-dev
Use PostCSS Color Functional Notation to process your CSS:
const postcssColorFunctionalNotation = require('postcss-color-functional-notation');
postcssColorFunctionalNotation.process(YOUR_CSS /*, processOptions, pluginOptions */);
Or use it as a PostCSS plugin:
const postcss = require('postcss');
const postcssColorFunctionalNotation = require('postcss-color-functional-notation');
postcss([
postcssColorFunctionalNotation(/* pluginOptions */)
]).process(YOUR_CSS /*, processOptions */);
PostCSS Color Functional Notation runs in all Node environments, with special instructions for:
| Node | PostCSS CLI | Webpack | Create React App | Gulp | Grunt |
|---|
Options
preserve
The preserve option determines whether the original functional color notation
is preserved. By default, it is not preserved.
postcssImageSetFunction({ preserve: true })
:root {
--firebrick: rgb(178 34 34);
--firebrick-a50: rgb(70% 13.5% 13.5% / 50%);
--firebrick-hsl: hsla(0 68% 42%);
--firebrick-hsl-a50: hsl(0 68% 42% / 50%);
}
/* becomes */
:root {
--firebrick: rgb(178, 34, 34);
--firebrick: rgb(178 34 34);
--firebrick-a50: rgba(178, 34, 34, .5);
--firebrick-a50: rgb(70% 13.5% 13.5% / 50%);
--firebrick-hsl: hsl(0, 68%, 42%);
--firebrick-hsl: hsla(0 68% 42%);
--firebrick-hsl-a50: hsla(0, 68%, 42%, .5);
--firebrick-hsl-a50: hsl(0 68% 42% / 50%);
}