I wanted set a custom color for an arrow w/ the mixin:
#popoverArrow > .top(5px, @red)
I couldn't because the color @black was hardcoded into the mixin.
I updated the mixins.less to allow custom colors for the popover arrow
added ability to set custom colors for popover arrow mixin
merge #2476 to allow for custom popover arrow colors
Merged into 2.0.2-wip. Thanks!