How to style for first-child of a certain type of element?

For example, I have HTML like :

<div class='page'>
    <span>2</span>
    <span>2</span>
    <a>1</a>
    <a>6</a>
</div>

How can I style for first child a

I used like this : .page a:first-child {color:red}

but it doesn't run.