Defining default values for Background color, text color, link color, padding and margin for custom blocks

block.json

{
	"$schema": "https://schemas.wp.org/trunk/block.json",
	"apiVersion": 2,
	"name": "create-block/block-supports-test",
	"version": "0.1.0",
	"title": "Block Supports Test",
	"category": "widgets",
	"icon": "smiley",
	"description": "Example block written with ESNext standard and JSX support – build step required.",
	"attributes":{
		"content": {
			"type": "string",
			"selector": "p"
		},
		"style": {
			"type": "object",
			"default": {
				"color": {
					"background": "#aabbcc",
					"text": "#00ff00"
				},
				"elements": {
					"link": {
						"color": {
							"text": "blue"
						}
					}
				},
				"spacing": {
					"padding": {
					  "top": "22px",
					  "right": "22px",
					  "bottom": "22px",
					  "left": "22px"
					},
					"margin": {
					  "top": "42px",
					  "right": "42px",
					  "bottom": "42px",
					  "left": "42px"
					}
				}
			}
		}
	},
	"supports": {
		"color": {
			"background": true,
			"text": true,
			"link": true
		},
		"spacing": {
			"margin":true,
			"padding": true
		}
	},
	"textdomain": "block-supports-test",
	"editorScript": "file:./index.js",
	"editorStyle": "file:./index.css",
	"style": "file:./style-index.css"
}