The following border utilities are meant to used in addition to those within primer-core.
Border Colors
White border with alpha transparency
Use .border-white-fade
to add a white border with an alpha transparency of 0.15. This is useful when you want a border that is a lighter shade of the background color. Additional border colors are available in primer-core border utilities.
<div class="bg-gray-dark text-white p-3 mb-2">
<span class="border border-white-fade p-2">
.border-white-fade .bg-gray-dark
</span>
</div>
<div class="bg-blue text-white p-3">
<span class="border border-white-fade p-2">
.border-white-fade .bg-blue
</span>
</div>