Sure, here is an example (standard HTML boilerplate omitted):
<svg id="svg1" xmlns="http://www.w3.org/2000/svg" style="width: 3.5in; height: 1in">
<circle id="circle1" r="30" cx="34" cy="34"
style="fill: red; stroke: blue; stroke-width: 2"/>
</svg>
<button onclick="circle1.style.fill="yellow";">Click to change to yellow</button>