Where To Put Your CSS SnippetExample modifying all FormsExample modifying one Form.More Info
Where To Put Your CSS Snippet
Refer to the article linked here for advice on where you can add this snippet](https://docs.gravityforms.com/where-to-put-your-custom-css/).
Example modifying all Forms
This will change the background color for all forms by using the form wrapper element
123body .gform_wrapper { background-color: yellow;}
Example modifying one Form.
This will target a specific form, in this case, form ID 1, as indicated by the extended element name. Refer to this article for the structure of element names.
123body #gform_wrapper_1 { background-color: yellow;}
More Info
See this article for dozens more examples of using CSS to target your form elements.