<!DOCTYPE html>
<style>
  #target::first-line { font-size: 150%; }
</style>

<div id="target"><span style='color:red'>red</span> <span style='color:green'>green</span> <span style='color:blue'>blue</span><br />
  <span style='color:red'>red</span> <span style='color:green'>green</span> <span style='color:blue'>blue</span>
</div>

<p>Both lines above (inside and outside <code>::first-line</code>) should have the same colors.</p>