diff --git a/__tests__/mergeConfigWithDefaults.test.js b/__tests__/resolveConfig.test.js
similarity index 66%
rename from __tests__/mergeConfigWithDefaults.test.js
rename to __tests__/resolveConfig.test.js
index f92bc94942ca..7ef2cbbe39e1 100644
--- a/__tests__/mergeConfigWithDefaults.test.js
+++ b/__tests__/resolveConfig.test.js
@@ -1,4 +1,4 @@
-import mergeConfigWithDefaults from '../src/util/mergeConfigWithDefaults'
+import resolveConfig from '../src/util/resolveConfig'
 
 test('prefix key overrides default prefix', () => {
   const userConfig = {
@@ -21,7 +21,7 @@ test('prefix key overrides default prefix', () => {
     },
   }
 
-  const result = mergeConfigWithDefaults(userConfig, defaultConfig)
+  const result = resolveConfig([userConfig, defaultConfig])
 
   expect(result).toEqual({
     prefix: 'tw-',
@@ -61,7 +61,7 @@ test('important key overrides default important', () => {
     },
   }
 
-  const result = mergeConfigWithDefaults(userConfig, defaultConfig)
+  const result = resolveConfig([userConfig, defaultConfig])
 
   expect(result).toEqual({
     prefix: '',
@@ -101,7 +101,7 @@ test('separator key overrides default separator', () => {
     },
   }
 
-  const result = mergeConfigWithDefaults(userConfig, defaultConfig)
+  const result = resolveConfig([userConfig, defaultConfig])
 
   expect(result).toEqual({
     prefix: '',
@@ -158,7 +158,7 @@ test('theme key is merged instead of replaced', () => {
     },
   }
 
-  const result = mergeConfigWithDefaults(userConfig, defaultConfig)
+  const result = resolveConfig([userConfig, defaultConfig])
 
   expect(result).toEqual({
     prefix: '-',
@@ -227,7 +227,7 @@ test('variants key is merged instead of replaced', () => {
     },
   }
 
-  const result = mergeConfigWithDefaults(userConfig, defaultConfig)
+  const result = resolveConfig([userConfig, defaultConfig])
 
   expect(result).toEqual({
     prefix: '-',
@@ -281,7 +281,7 @@ test('missing top level keys are pulled from the default config', () => {
     },
   }
 
-  const result = mergeConfigWithDefaults(userConfig, defaultConfig)
+  const result = resolveConfig([userConfig, defaultConfig])
 
   expect(result).toEqual({
     prefix: '-',
@@ -300,3 +300,133 @@ test('missing top level keys are pulled from the default config', () => {
     },
   })
 })
+
+test('functions in the default theme section are lazily evaluated', () => {
+  const userConfig = {
+    theme: {
+      colors: {
+        red: 'red',
+        green: 'green',
+        blue: 'blue',
+      },
+    },
+  }
+
+  const defaultConfig = {
+    prefix: '-',
+    important: false,
+    separator: ':',
+    theme: {
+      colors: {
+        cyan: 'cyan',
+        magenta: 'magenta',
+        yellow: 'yellow',
+      },
+      backgroundColors: ({ colors }) => colors,
+      textColors: ({ colors }) => colors,
+    },
+    variants: {
+      backgroundColors: ['responsive', 'hover', 'focus'],
+      textColors: ['responsive', 'hover', 'focus'],
+    },
+  }
+
+  const result = resolveConfig([userConfig, defaultConfig])
+
+  expect(result).toEqual({
+    prefix: '-',
+    important: false,
+    separator: ':',
+    theme: {
+      colors: {
+        red: 'red',
+        green: 'green',
+        blue: 'blue',
+      },
+      backgroundColors: {
+        red: 'red',
+        green: 'green',
+        blue: 'blue',
+      },
+      textColors: {
+        red: 'red',
+        green: 'green',
+        blue: 'blue',
+      },
+    },
+    variants: {
+      backgroundColors: ['responsive', 'hover', 'focus'],
+      textColors: ['responsive', 'hover', 'focus'],
+    },
+  })
+})
+
+test('functions in the user theme section are lazily evaluated', () => {
+  const userConfig = {
+    theme: {
+      colors: {
+        red: 'red',
+        green: 'green',
+        blue: 'blue',
+      },
+      backgroundColors: ({ colors }) => ({
+        ...colors,
+        customBackground: '#bada55',
+      }),
+      textColors: ({ colors }) => ({
+        ...colors,
+        customText: '#facade',
+      }),
+    },
+  }
+
+  const defaultConfig = {
+    prefix: '-',
+    important: false,
+    separator: ':',
+    theme: {
+      colors: {
+        cyan: 'cyan',
+        magenta: 'magenta',
+        yellow: 'yellow',
+      },
+      backgroundColors: ({ colors }) => colors,
+      textColors: ({ colors }) => colors,
+    },
+    variants: {
+      backgroundColors: ['responsive', 'hover', 'focus'],
+      textColors: ['responsive', 'hover', 'focus'],
+    },
+  }
+
+  const result = resolveConfig([userConfig, defaultConfig])
+
+  expect(result).toEqual({
+    prefix: '-',
+    important: false,
+    separator: ':',
+    theme: {
+      colors: {
+        red: 'red',
+        green: 'green',
+        blue: 'blue',
+      },
+      backgroundColors: {
+        red: 'red',
+        green: 'green',
+        blue: 'blue',
+        customBackground: '#bada55',
+      },
+      textColors: {
+        red: 'red',
+        green: 'green',
+        blue: 'blue',
+        customText: '#facade',
+      },
+    },
+    variants: {
+      backgroundColors: ['responsive', 'hover', 'focus'],
+      textColors: ['responsive', 'hover', 'focus'],
+    },
+  })
+})
diff --git a/defaultTheme.js b/defaultTheme.js
index 791879b98ff3..a6ae404619ed 100644
--- a/defaultTheme.js
+++ b/defaultTheme.js
@@ -1,92 +1,90 @@
 module.exports = function() {
-  const colors = {
-    transparent: 'transparent',
-
-    black: '#22292f',
-    'grey-darkest': '#3d4852',
-    'grey-darker': '#606f7b',
-    'grey-dark': '#8795a1',
-    grey: '#b8c2cc',
-    'grey-light': '#dae1e7',
-    'grey-lighter': '#f1f5f8',
-    'grey-lightest': '#f8fafc',
-    white: '#ffffff',
+  return {
+    colors: {
+      transparent: 'transparent',
 
-    'red-darkest': '#3b0d0c',
-    'red-darker': '#621b18',
-    'red-dark': '#cc1f1a',
-    red: '#e3342f',
-    'red-light': '#ef5753',
-    'red-lighter': '#f9acaa',
-    'red-lightest': '#fcebea',
+      black: '#22292f',
+      'grey-darkest': '#3d4852',
+      'grey-darker': '#606f7b',
+      'grey-dark': '#8795a1',
+      grey: '#b8c2cc',
+      'grey-light': '#dae1e7',
+      'grey-lighter': '#f1f5f8',
+      'grey-lightest': '#f8fafc',
+      white: '#ffffff',
 
-    'orange-darkest': '#462a16',
-    'orange-darker': '#613b1f',
-    'orange-dark': '#de751f',
-    orange: '#f6993f',
-    'orange-light': '#faad63',
-    'orange-lighter': '#fcd9b6',
-    'orange-lightest': '#fff5eb',
+      'red-darkest': '#3b0d0c',
+      'red-darker': '#621b18',
+      'red-dark': '#cc1f1a',
+      red: '#e3342f',
+      'red-light': '#ef5753',
+      'red-lighter': '#f9acaa',
+      'red-lightest': '#fcebea',
 
-    'yellow-darkest': '#453411',
-    'yellow-darker': '#684f1d',
-    'yellow-dark': '#f2d024',
-    yellow: '#ffed4a',
-    'yellow-light': '#fff382',
-    'yellow-lighter': '#fff9c2',
-    'yellow-lightest': '#fcfbeb',
+      'orange-darkest': '#462a16',
+      'orange-darker': '#613b1f',
+      'orange-dark': '#de751f',
+      orange: '#f6993f',
+      'orange-light': '#faad63',
+      'orange-lighter': '#fcd9b6',
+      'orange-lightest': '#fff5eb',
 
-    'green-darkest': '#0f2f21',
-    'green-darker': '#1a4731',
-    'green-dark': '#1f9d55',
-    green: '#38c172',
-    'green-light': '#51d88a',
-    'green-lighter': '#a2f5bf',
-    'green-lightest': '#e3fcec',
+      'yellow-darkest': '#453411',
+      'yellow-darker': '#684f1d',
+      'yellow-dark': '#f2d024',
+      yellow: '#ffed4a',
+      'yellow-light': '#fff382',
+      'yellow-lighter': '#fff9c2',
+      'yellow-lightest': '#fcfbeb',
 
-    'teal-darkest': '#0d3331',
-    'teal-darker': '#20504f',
-    'teal-dark': '#38a89d',
-    teal: '#4dc0b5',
-    'teal-light': '#64d5ca',
-    'teal-lighter': '#a0f0ed',
-    'teal-lightest': '#e8fffe',
+      'green-darkest': '#0f2f21',
+      'green-darker': '#1a4731',
+      'green-dark': '#1f9d55',
+      green: '#38c172',
+      'green-light': '#51d88a',
+      'green-lighter': '#a2f5bf',
+      'green-lightest': '#e3fcec',
 
-    'blue-darkest': '#12283a',
-    'blue-darker': '#1c3d5a',
-    'blue-dark': '#2779bd',
-    blue: '#3490dc',
-    'blue-light': '#6cb2eb',
-    'blue-lighter': '#bcdefa',
-    'blue-lightest': '#eff8ff',
+      'teal-darkest': '#0d3331',
+      'teal-darker': '#20504f',
+      'teal-dark': '#38a89d',
+      teal: '#4dc0b5',
+      'teal-light': '#64d5ca',
+      'teal-lighter': '#a0f0ed',
+      'teal-lightest': '#e8fffe',
 
-    'indigo-darkest': '#191e38',
-    'indigo-darker': '#2f365f',
-    'indigo-dark': '#5661b3',
-    indigo: '#6574cd',
-    'indigo-light': '#7886d7',
-    'indigo-lighter': '#b2b7ff',
-    'indigo-lightest': '#e6e8ff',
+      'blue-darkest': '#12283a',
+      'blue-darker': '#1c3d5a',
+      'blue-dark': '#2779bd',
+      blue: '#3490dc',
+      'blue-light': '#6cb2eb',
+      'blue-lighter': '#bcdefa',
+      'blue-lightest': '#eff8ff',
 
-    'purple-darkest': '#21183c',
-    'purple-darker': '#382b5f',
-    'purple-dark': '#794acf',
-    purple: '#9561e2',
-    'purple-light': '#a779e9',
-    'purple-lighter': '#d6bbfc',
-    'purple-lightest': '#f3ebff',
+      'indigo-darkest': '#191e38',
+      'indigo-darker': '#2f365f',
+      'indigo-dark': '#5661b3',
+      indigo: '#6574cd',
+      'indigo-light': '#7886d7',
+      'indigo-lighter': '#b2b7ff',
+      'indigo-lightest': '#e6e8ff',
 
-    'pink-darkest': '#451225',
-    'pink-darker': '#6f213f',
-    'pink-dark': '#eb5286',
-    pink: '#f66d9b',
-    'pink-light': '#fa7ea8',
-    'pink-lighter': '#ffbbca',
-    'pink-lightest': '#ffebef',
-  }
+      'purple-darkest': '#21183c',
+      'purple-darker': '#382b5f',
+      'purple-dark': '#794acf',
+      purple: '#9561e2',
+      'purple-light': '#a779e9',
+      'purple-lighter': '#d6bbfc',
+      'purple-lightest': '#f3ebff',
 
-  return {
-    colors,
+      'pink-darkest': '#451225',
+      'pink-darker': '#6f213f',
+      'pink-dark': '#eb5286',
+      pink: '#f66d9b',
+      'pink-light': '#fa7ea8',
+      'pink-lighter': '#ffbbca',
+      'pink-lightest': '#ffebef',
+    },
     screens: {
       sm: '576px',
       md: '768px',
@@ -155,8 +153,8 @@ module.exports = function() {
       normal: '0',
       wide: '0.05em',
     },
-    textColors: colors,
-    backgroundColors: colors,
+    textColors: theme => theme.colors,
+    backgroundColors: theme => theme.colors,
     backgroundSize: {
       auto: 'auto',
       cover: 'cover',
@@ -169,7 +167,9 @@ module.exports = function() {
       '4': '4px',
       '8': '8px',
     },
-    borderColors: global.Object.assign({ default: colors['grey-light'] }, colors),
+    borderColors: theme => {
+      return global.Object.assign({ default: theme.colors['grey-light'] }, theme.colors)
+    },
     borderRadius: {
       none: '0',
       sm: '.125rem',
diff --git a/src/index.js b/src/index.js
index 1cdf2525661d..1985aee55391 100644
--- a/src/index.js
+++ b/src/index.js
@@ -6,7 +6,7 @@ import perfectionist from 'perfectionist'
 
 import registerConfigAsDependency from './lib/registerConfigAsDependency'
 import processTailwindFeatures from './processTailwindFeatures'
-import mergeConfigWithDefaults from './util/mergeConfigWithDefaults'
+import resolveConfig from './util/resolveConfig'
 
 const plugin = postcss.plugin('tailwind', config => {
   const plugins = []
@@ -17,17 +17,17 @@ const plugin = postcss.plugin('tailwind', config => {
 
   const getConfig = () => {
     if (_.isUndefined(config)) {
-      return require('../defaultConfig')()
+      return resolveConfig([require('../defaultConfig')()])
     }
 
     if (!_.isObject(config)) {
       delete require.cache[require.resolve(path.resolve(config))]
     }
 
-    return mergeConfigWithDefaults(
+    return resolveConfig([
       _.isObject(config) ? config : require(path.resolve(config)),
-      require('../defaultConfig')()
-    )
+      require('../defaultConfig')(),
+    ])
   }
 
   return postcss([
diff --git a/src/util/mergeConfigWithDefaults.js b/src/util/mergeConfigWithDefaults.js
deleted file mode 100644
index fac9dbb32beb..000000000000
--- a/src/util/mergeConfigWithDefaults.js
+++ /dev/null
@@ -1,12 +0,0 @@
-import _ from 'lodash'
-
-export default function(userConfig, defaultConfig) {
-  return _.defaults(
-    {
-      theme: _.defaults(userConfig.theme, defaultConfig.theme),
-      variants: _.defaults(userConfig.variants, defaultConfig.variants),
-    },
-    userConfig,
-    defaultConfig
-  )
-}
diff --git a/src/util/resolveConfig.js b/src/util/resolveConfig.js
new file mode 100644
index 000000000000..2f16773070f4
--- /dev/null
+++ b/src/util/resolveConfig.js
@@ -0,0 +1,20 @@
+import _ from 'lodash'
+
+function resolveFunctionKeys(object) {
+  return Object.keys(object).reduce((resolved, key) => {
+    return {
+      ...resolved,
+      [key]: _.isFunction(object[key]) ? object[key](object) : object[key],
+    }
+  }, {})
+}
+
+export default function(configs) {
+  return _.defaults(
+    {
+      theme: resolveFunctionKeys(_.defaults(..._.map(configs, 'theme'))),
+      variants: _.defaults(..._.map(configs, 'variants')),
+    },
+    ...configs
+  )
+}