Example dark section style

section-dark.json

{
	"$schema": "https://schemas.wp.org/trunk/theme.json",
	"version": 3,
	"title": "Section Dark Mode",
	"slug": "section-dark",
	"blockTypes": ["core/group"],
	"styles": {
		"color": {
			"background": "var:preset|color|foreground",
			"text": "var:preset|color|background"
		},
		"elements": {
			"button": {
				"color": {
					"text": "var:preset|color|primary"
				},
				"border":{
					"color": "var:preset|color|primary"
				},
				":hover": {
					"color": {
						"background": "var:preset|color|background"
					}
				}
			},
			"h3":{
				"color" : {
					"text": "var:preset|color|primary"
				}
			},
			"link": {
				"color": {
					"text": "var:preset|color|tertiary"
				},
				":hover": {
					"color": {
						"text": "var:preset|color|tertiary"
					}
				}
			}
		}
	}
}