Tailwind CSS: Referencing Theme Colors When Creating Custom Class

Question

I am trying to modify the tailwind.config.js file to create some custom classes. For example, I would like to create a color palette - and do so by referencing other colors in the theme.

To do so, I have made the following changes to the tailwind.config.js file:

module.exports = {
  theme: {
    extend: {
      colors: {
        primary: (theme) => theme("colors.blue.500"),
      },
    }
    ...

This, however, does not work. I don't get any errors - but I also do not get any custom classes either (even though, according to the docs, this should work).

On the other hand, this does work:

module.exports = {
  theme: {
    extend: {
      colors: {
        primary: "#abcdef",
      },
    }
    ...

This will create classes such as bg-primary.

Any idea how I can create custom classes by referncing other values in the theme?

Thanks.

Matias Kinnunen Matias Kinnunen · Accepted Answer · 2020-07-04T17:49:52

Your first example indeed doesn't seem to work. These don't work either:

module.exports = {
  theme: {
    extend: {
      colors: (theme) => ({
        primary: theme('colors.blue.500'),
      })
    },
  },
}
// → RangeError: Maximum call stack size exceeded

module.exports = {
  theme: {
    extend: (theme) => ({
      colors: {
        primary: theme('colors.blue.500'),
      }
    }),
  },
}
// → no error, but doesn't work

module.exports = {
  theme: (theme) => ({
    extend: {
      colors: {
        primary: theme('colors.blue.500'),
      }
    },
  }),
}
// → no error, but doesn't work

However, the Customizing Colors page has a section called Overriding a single shade which contains the following example and explanation why your config and my configs above don't work:

Since values in the theme.extend section of your config file are only merged shallowly, overriding a single shade is slightly more complicated.

The easiest option is to import the default theme and spread in the color you want to customize along with the new shade value:
// tailwind.config.js
const { colors } = require('tailwindcss/defaultTheme')

module.exports = {
  theme: {
    extend: {
      colors: {
        blue: {
          ...colors.blue,
          '900': '#1e3656',
        }
      }
    }
  }
}

So, here's how you can achieve what you are trying to do:

const { colors } = require('tailwindcss/defaultTheme')

module.exports = {
  theme: {
    extend: {
      colors: {
        primary: colors.blue['500'], // 500 (number) would also work
      }
    }
  }
}

I tried this, and it seems to work. The built CSS file contains these classes (among others, of course):

.bg-blue-500 {
  --bg-opacity: 1;
  background-color: #4299e1;
  background-color: rgba(66, 153, 225, var(--bg-opacity));
}

.bg-primary {
  --bg-opacity: 1;
  background-color: #4299e1;
  background-color: rgba(66, 153, 225, var(--bg-opacity));
}

Tailwind CSS: Referencing Theme Colors When Creating Custom Class

1 Answers