div.stub * { color : lime }
div.stub > * > *:not(:active) { color : black }
<div xmlns="http://www.w3.org/1999/xhtml" class="stub">
<p>
<a href="http://dummy.example.org/dummy">This is an anchor</a>
</p>
<p>
<button>The color of the anchor above and the current text should be
black in normal state, and green when you make it active.</button>
</p>
</div>