How to add custom opacity values to colors in tailwind css themes

Question

I am trying to learn how to do themes in tailwind CSS for a laravel project. Stuck on how to add opacity in the theme

//app.css file

@layer base {
    :root {
        /* Brand Color */
        --color-element-primary: #5754FF;
        --color-element-soft-hover: #5754FF; /* 15% */

        /* Text */
        --color-text-primary: #FFFFFF;
        --color-text-content:#FFFFFF; /* 80% */
        --color-text-muted:#7C879F; /* 45% */

Than in the tailwind.config.js file I setup things like this

extend: {
            fontFamily: {
                sans: ["General Sans", ...defaultTheme.fontFamily.sans],
            },
            colors: {
                theme: {
                    'primary': 'var(--color-element-primary)',
                    'primary-soft-hover': 'var(--color-element-primary-soft-hover)',

                }
            },
            textColor: {
                theme: {
                    primary: 'var(--color-text-primary)',
                    content: 'var(--color-text-content)',
                    muted: 'var(--color-text-muted)',
                }
            },

This allows me to use it inside the project like this

But I want to make the opacity values dynamic to the themes. Any insight on how to set this up is much appreciated :)

Answer 1

I was looking to use the a theme color with opacity utilities (like bg-primary/25) from the framework. Not sure if that is the question here?

In case it is I came across this functions, which works for me:

const getColor = (colorVar, { opacityVariable, opacityValue }) => {
  if (opacityValue !== undefined) {
    return `rgb(var(${colorVar})/${opacityValue})`;
  }
  if (opacityVariable !== undefined) {
    return `rgb(var(${colorVar})/var(${opacityVariable}, 1))`;
  }

  return `rgb(var(${colorVar}))`;
};

and apply it like so in your source tailwind.config.js

theme: {
  colors: {
    primary: (params) => getColor("--color-primary", params)
  }
}

Now you can define the --color-primary variable in your css file and it will change accordingly.