Loop through JSON object in Twig from the database
You'll simply need to decode the JSON string. Unfortunately, Twig doesn't ship with a json_decode filter, but there's a plugin. 

Here's how you'd use it:

&lt;ul&gt;
{% for block in entry.gridcontrol|json_decode %}
  {% set entry = craft.entries.id(block.id) %}
  &lt;li class="{{ block.classes }}" style="left:{{ block.x }}%"&gt;
    {{ entry.title }}
  &lt;/li&gt;
{% endfor %}
&lt;ul&gt;