Is there a way to set a form back to not having a theme?

Is there a way to unset a theme? I.e. I liked the way it looked before it had a theme better, but I don't see an option for removing the theme - only options to use a different theme. 

Hi,

There are several methods you can do to remove a theme;

Method 1. Set the theme to Default in your Form Builder's Preference

Method 2: Remove the Custom css from the settings. Here's how you can access the css area: 
How to Inject Custom CSS Codes

Method 3: You can revert your form to the original state using your revision history.

For more information about form revisions: Introducing Form Revisions Never Lose Your Work Again

Do inform us if you need further assistance,
Regards.