SCSS for re-styling https://wordpress.org/plugins/widget-countdown/

timer.scss

$text-color: #e4a923;
$font-main: 'Oswald', sans-serif;

@mixin font-geometry-base($font-size) {
  font-size: $font-size;
  line-height: $font-size * 1.667;
}

.countdown-outer {
  .heading {
    @include font-geometry-base(21px);
    text-transform: uppercase;
    font-size: 21px;
    line-height: 35px;
    color: #222222;
  }
}

.content_countdown#main_countedown_1 {
  .countdown {
    span.element_conteiner {
      min-width: 90px;
      margin: 0 6px;

      .time_left {
        color: $text-color;
        font-family: $font-main;
        font-weight: normal;
        background: none !important;
        border: 1px solid $text-color;
        border-radius: 6px;
      }
      .time_description {
        color: $text-color;
        font-family: $font-main;
        font-weight: normal;
      }
    }
  }
}