This example demonstrates the simplest possible way to use D3.js to modify an HTML page. It selects the first `<h1>` heading on the page using `d3.select('h1')` and sets its CSS `color` property to red via the `.style()` method. The visualization relies on the D3 v4 framework, loaded from a CDN, and is contained within a basic HTML file with linked CSS and JavaScript files. It shows how D3 can be used for basic DOM manipulation and styling without any data or complex rendering.