example: standard paragraph field (textarea) – applies to all forms
body .gform_wrapper .gform_body .gform_fields .gfield textarea {border: 1px solid red}
example: standard paragraph field (textarea) – applies just to form ID #1
body #gform_wrapper_1 .gform_body .gform_fields .gfield textarea {border: 1px solid red}
example: standard paragraph field (textarea) – applies just to specific paragraph field (based on the unique parent element ID – replace 「XX_X」 with your actual element ID)
body .gform_wrapper .gform_body .gform_fields #field_XX_X.gfield textarea {border: 1px solid red}