mdb-ui-kit/scss/_tabs.scss

.nav-tabs {
  background: $brand-primary;
  > li {
    > a {
      margin: 0;
      color: $white;
      border: 0;
      &:hover {
        background-color: transparent;
        border: 0;
      }
    }
    > a,
    > a:hover,
    > a:focus {
      font-weight: 500;
      color: $white !important;
      background-color: transparent !important;
      border: 0 !important;
    }
    &.disabled > a, &.disabled > a:hover {
      color: rgba($white, 0.5);
    }
  }

}