diff -r 4b780ebbedc6 -r 0e6703cd0968 client/src/components/SlateEditor/HtmlSerializer.js
--- a/client/src/components/SlateEditor/HtmlSerializer.js	Tue Nov 13 16:46:15 2018 +0100
+++ b/client/src/components/SlateEditor/HtmlSerializer.js	Fri Nov 16 11:19:13 2018 +0100
@@ -65,7 +65,7 @@
         case 'underlined':
           return <ins>{children}</ins>
         case 'category':
-          return <span style={{ backgroundColor: obj.color }}>{children}</span>
+          return <span style={{ backgroundColor: obj.data.get('color') }}>{children}</span>
         default: return;
       }
     }