<svg width="100%" height="300" xmlns="https://www.w3.org/2000/svg" xmlns:xlink="https://www.w3.org/1999/xlink" viewBox='0 0 50 100'>
<style>
.classA { fill:red }
</style>
<defs>
<g id="Port">
<circle style="fill:inherit" r="10"/>
</g>
</defs>
<text y="15">black</text>
<use x="50" y="10" xlink:href="#Port" />
<text y="35">red</text>
<use x="50" y="30" xlink:href="#Port" class="classA"/>
<text y="55">blue</text>
<use x="50" y="50" xlink:href="#Port" style="fill:blue"/>
</svg>