import Head from 'next/head';

export default () =>
  <header>
    <Head>
      <style global jsx>{`
        body {
          font-family: "Helvetica Neue", Arial, sans-serif;
          color: ##5d5d5d;
        }
        a {
          text-decoration: none;
          color: #03a9f4;
        }
      `}</style>
    </Head>
  </header>;

import Head from 'next/head';

export default () =>
  <header>
    <Head>
      <style global jsx>{`
        body {
          font-family: "Helvetica Neue", Arial, sans-serif;
        }
      `}</style>
    </Head>
  </header>;

--- 
+++ 
@@ -6,6 +6,11 @@
       <style global jsx>{`
         body {
           font-family: "Helvetica Neue", Arial, sans-serif;
+          color: ##5d5d5d;
+        }
+        a {
+          text-decoration: none;
+          color: #03a9f4;
         }
       `}</style>
     </Head>
Add global text and link styling