<h1 class="cp_h1title">見出しテキスト</h1>

.cp_h1title {
  position: relative;
  border-bottom: 1px solid #26C6DA;/*下の線*/
  padding: 0 0 0 12px;
}
.cp_h1title::before,
.cp_h1title::after {
  position: absolute;
  content: '';
  bottom: 0;
  left: 0;
  width: 6px;/*左線の太さ*/
}
.cp_h1title::before {
  height: 100%;/*左線長い線の長さ*/
  background-color: #26C6DA;/*左線長い線の色（上の色）*/
}
.cp_h1title::after {
  height: 50%;/*左線短い線の長さ*/
  background-color: #1A237E;/*左線短い線の色（下の色）*/
}