Remove duplicate colours

Same as in the defaults.

tailwind.js

@@ -2,17 +2,13 @@ let defaultConfig = require('tailwindcss/defaultConfig')()
 
 var colors = {
   ...defaultConfig.colors,
-  'black': '#22292f',
   'green': '#bada55',
-  'grey': '#b8c2cc',
   'grey-dark': '#303030',
   'grey-darkest': '#1e1d1d',
   'grey-lightest': '#eae9ea',
   'red': '#a42e27',
   'red-90': 'rgba(164, 46, 39, .9)',
   'red-dark': '#3a1d19',
-  'transparent': 'transparent',
-  'white': '#ffffff',
 }
 
 module.exports = {