<!doctype html>
<html>
<head>
<style>
.container {
    border:1px solid black;
}
.container>.number {
    color:red;
}
.container>.letters {
    color:blue;
}
</style>
</head>
<body>
<div id="test1">
  <div class="number">1</div>
  <div class="letters">QUX</div>
</div>

<div id="test2">
  <div class="container">
    <div class="number"><div class="number">2</div></div>
    <div class="letters"><div class="letters">FOO</div></div>
  </div>
</div>

<div id="test3">
  <div class="number">3</div>
  <div class="letters">BAR</div>
</div>
</body>
</html>