I understand your concern but to change such styling you need to add fields manually:
%%FORM_DATA%% is a placeholder and its a string so you do not have any control to change any style there.
If you want to change such style, you need to design your output I mean you need to format the whole post body with lable and fields and add
your required style accordingly:
For example:
thats not really a solution. Replacing a Placeholder/Shortcode with manually created output for each field is not an option. but i get that there isn't really a way to style the output of the placeholders. would be a suggestion for the future 🙂
But it's not really that much of an issue. in our case, the customer prints every email, so the background is moisting the sheets.... but i'll tell him that he has to live with it..