Hi,
Thank you for reaching out to us.
The form design can be customized through CSS. There are two recommended ways:
1. Write CSS that overwrites our Profile Builder styling directly in your theme. You can then target just the elements that interest you.
2. Copy the css found inside wp-content\plugins\profile-builder\assets\css\style-front-end.css directly in your theme and disable Profile Builder to load it’s own css.
If needed, you can also install Custom CSS Classes on Fields, a free add-on that lets you add CSS classes to individual fields. You can install it directly from your Dashboard, from Profile Builder -> Add-ons.
What we don’t recommend is starting from scratch and try to re-do all the CSS. Unless you have a particular need to do it like that, I would recommend the above.
Best regards,