<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">
<defs>
<pattern id="green" x="0" y="0" width="100" height="100">
<rect x="0" y="0" width="100" height="100" fill="green"/>
</pattern>
</defs>
<rect x="0" y="0" width="100" height="100" fill="red" />
<rect x="0" y="0" width="100" height="100" fill="url(#green)" />
</svg>