theme.json

theme.json

{
    "version": 1,
    "settings": {
        "layout": {
            "contentSize": "800px",
            "wideSize": "1000px"
        },
        "border": {
            "customColor": false,
            "customRadius": false,
            "customStyle": false,
            "customWidth": false
        },
        "color": {
            "custom": false,
            "customGradient": false,
            "link": false,
            "palette": [
                {
                    "name": "Black",
                    "slug": "black",
                    "color": "#000000"
                },
                {
                    "name": "White",
                    "slug": "white",
                    "color": "#ffffff"
                }
            ],
            "gradients": [
                {
				    "slug": "black-to-white",
					"gradient": "linear-gradient(160deg, var(--wp--preset--color--black), var(--wp--preset--color--white))",
					"name": "Black to White"
				},
				{
					"slug": "white-to-black",
					"gradient": "linear-gradient(160deg, var(--wp--preset--color--white), var(--wp--preset--color--black))",
					"name": "White to Black"
				}
            ],
            "duotone": [
                {
					"slug": "black-and-white",
					"colors": [
                        "#000000",
                        "#ffffff"
                    ],
					"name": "Black and White"
				},
				{
					"slug": "white-and-black",
					"colors": [
                        "#ffffff",
                        "#000000"
                    ],
					"name": "White and Black"
				}
            ]
        },
        "typography": {
            "customFontSize": false,
            "customFontStyle": false,
            "customFontWeight": false,
            "customLineHeight": false,
            "customTextDecorations": false,
            "customTextTransforms": false,
            "dropCap": false,
            "fontFamilies": [
				{
					"fontFamily": "Helvetica Neue, Helvetica, Arial, sans-serif",
					"slug": "helvetica-arial"
				},
				{
					"fontFamily": "Geneva, Tahoma, Verdana, sans-serif",
					"slug": "geneva-verdana"
				}
            ],
            "fontSizes": [
				{
					"slug": "small",
					"size": "18px",
					"name": "Small"
				},
				{
					"slug": "large",
					"size": "24px",
					"name": "Large"
				}
            ]
        }
    }
}

Note that duotone presets cannot use the variables set in the color palette. Hex, RGB and named HTML colors should work. The gist has been updated to use hex codes instead of named colors to remove some confusion but the previous version of the file did work correctly.