Once you’ve set your form field as readonly, you can style it differently from the other read & write fields with Microthemer by enabling the :read-only pseudo selector when targeting the element:
Note: I’ve just noticed that Microthemer requires the readonly attribute to be added with the following syntax:
(rather than just readonly by itself)
This will be fixed in the next day or two. I’ve already updated my development version of Microthemer, but I need to finish some other updates I’m half way through before rolling out an update. I hope that’s OK.