Every form used to look the same; only the brand colour differed. Under Appearance you now choose from five styles: Outlined (as it was), Underline, Filled, Rounded and Sharp. Underline draws only a line under each field, puts the labels in widely spaced capitals and writes "(optional)" after the questions that are not required.
You can then refine a style: the fields' border, border colour, fill, corners and height, the labels' weight and size, the button's shape and width, and the space between questions. Colour, typeface and corners still come from your branding.
"Copy style from…" takes the style of another form. In your branding you set a default style that new forms follow; an existing form follows it once you turn on "Follow the branding".
A dark form on a dark site no longer draws dark surfaces of its own: your site's background shows through.