<ol class="cp_clist">
  <li>css</li>
  <li>html</li>
  <li>copy</li>
  <li>easy</li>
</ol>

ol.cp_clist {
  padding: 0;
  counter-reset:cp_clist; /*数字をリセット*/
  list-style-type: none;
}
ol.cp_clist li {
  position: relative;
  display: flex;
  align-items: center;
  margin: 10px;
  padding: 0 10px 0 40px;
  min-height: 30px;
  border: 1px dotted #f1c6c6;
  transition: 0.3s;
}
ol.cp_clist li:nth-child(4n+2){
  border-color:#8cd9bc;
}
ol.cp_clist li:nth-child(4n+3){
  border-color:#9575CD;
}
ol.cp_clist li:nth-child(4n+4){
  border-color:#f8e5ab;
}
ol.cp_clist li:before {
  position: absolute;
  left: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  /* カウントさせる */
  counter-increment: cp_clist;
  content: counter(cp_clist);
  /*装飾*/
  color: #fff;
  width: 30px;
  height: 30px;
}
ol.cp_clist li:nth-child(4n+1):before{
  background: #F06292;
}
ol.cp_clist li:nth-child(4n+2):before{
  background: #4DB6AC;
}
ol.cp_clist li:nth-child(4n+3):before{
  background: #9575CD;
}
ol.cp_clist li:nth-child(4n+4):before{
  background: #FFB74D;
}
/*hover時の設定*/
ol.cp_clist li:hover {
  color:#fff;
}
ol.cp_clist li:nth-child(4n+1):hover{
  background: #F06292;
}
ol.cp_clist li:nth-child(4n+1):hover:before{
  background: #fff;
  color: #F06292;
}
ol.cp_clist li:nth-child(4n+2):hover{
  background: #4DB6AC;
}
ol.cp_clist li:nth-child(4n+2):hover:before{
  background: #fff;
  color: #4DB6AC;
}
ol.cp_clist li:nth-child(4n+3):hover{
  background: #9575CD;
}
ol.cp_clist li:nth-child(4n+3):hover:before{
  background: #fff;
  color: #9575CD;
}
ol.cp_clist li:nth-child(4n+4):hover{
  background: #FFB74D;
}
ol.cp_clist li:nth-child(4n+4):hover:before{
  background: #fff;
  color: #FFB74D;
}