mdb-ui-kit/scss/_nav.scss

// https://www.google.com/design/spec/components/tabs.html#tabs-specs

.nav { // base for tabs and pills
  font-size: $mdb-nav-font-size;
  font-weight: $mdb-nav-font-weight;
}

.nav-link {
  //line-height: $mdb-nav-link-line-height; // set baseline line-height and font sizes
  text-transform: uppercase;
}

.nav-tabs,
.nav-pills {
  border: 0;

  .nav-link {
    padding: $mdb-nav-tabs-link-padding;
    border: 0;
  }
}

.nav-tabs {
  .nav-link {
    border-bottom: $mdb-nav-tabs-border-size solid transparent;
  }

  // colors
  @include mdb-tabs-color($mdb-nav-tabs-color, $mdb-nav-tabs-active-color, $mdb-nav-tabs-active-border-color, $mdb-nav-tabs-disabled-link-color, $mdb-nav-tabs-disabled-link-color-hover);

  &.bg-primary {
    @include mdb-tabs-color($mdb-nav-tabs-primary-color, $mdb-nav-tabs-primary-active-color, $mdb-nav-tabs-primary-active-border-color, $mdb-nav-tabs-primary-disabled-link-color, $mdb-nav-tabs-primary-disabled-link-color-hover);
  }

  &.bg-inverse {
    @include mdb-tabs-color($mdb-nav-tabs-inverse-color, $mdb-nav-tabs-inverse-active-color, $mdb-nav-tabs-inverse-active-border-color, $mdb-nav-tabs-inverse-disabled-link-color, $mdb-nav-tabs-inverse-disabled-link-color-hover);
  }
}