change button border color css code example
Example: button style css
<button class="pure-button">
<i class="fa fa-cog"></i>Settings
</button>
<a class="pure-button" href="#">
<i class="fa fa-shopping-cart fa-lg"></i>Checkout
</a>
<button class="pure-button">
<i class="fa fa-cog"></i>Settings
</button>
<a class="pure-button" href="#">
<i class="fa fa-shopping-cart fa-lg"></i>Checkout
</a>