css/modules/primer-breadcrumb/lib/breadcrumb.scss

.breadcrumb-item {
  display: inline-block;
  margin-left: -0.35em;
  white-space: nowrap;
  list-style: none;

  &::after {
    padding-right: 0.5em;
    padding-left: 0.5em;
    color: $border-gray;
    content: "/";
  }

  &:first-child {
    margin-left: 0;
  }
}

.breadcrumb-item-selected {
  &::after {
    content: none;
  }
}