It’s body {}, it addresses the whole html body (everything) and is empty in this case. It’s probably just an example.

Hi,

I just saw that you already opened an issue on GitHub and answered there so that the developer get’s a notification, too.

Meanwhile, you can edit the module yourself like this:

Change line 103 in MMM-MQTT.js from
valueWrapper.className = "align-right bright medium";
to
valueWrapper.className = "align-right bright medium " + sub.value.toLowerCase();

provided the value is just one word, not more, the cell with the value now has a class name added that’s the same as the value, in your case ‘closed’ and you can add the following to the CSS file or your custom.css:
.MMM-MQTT .closed { color: green; } .MMM-MQTT .open{ color: red; }

Regards,
Torben