Example: Changing Your Form’s Background Color

Example modifying all forms

This will change the background color for all forms by using the form wrapper element

body .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.

body #gform_wrapper_1 {
    background-color: yellow;
}

Placement

You can add your Custom CSS to the Customizer (Appearance → Customize) or your child theme stylesheet.

See also: Where to Put your Custom CSS.

More Info

See this article for dozens more examples of using CSS to target your form elements.