demo/src/app/components/+popover/demos/styling-global/styling-global.html
<style>
.popover {
background-color: #7B1FA2;
color: #fff;
}
.popover>.arrow:after {
border-top-color: #7B1FA2 !important;
}
</style>
<button type="button" class="btn btn-success"
popover="Vivamus sagittis lacus vel augue laoreet rutrum faucibus.">
I was globally styled
</button>