如何使用CSS修改选择框样式

<div class="cp_ipselect cp_sl04">
  <select required>
    <option value="" hidden>请选择具体位置</option>
    <option value="1">合肥</option>
    <option value="2">南京</option>
    <option value="3">芜湖</option>
    <option value="4">上海</option>
  </select>
</div>

.cp_ipselect {
  overflow: hidden;
  width: 90%;
  margin: 2em auto;
  text-align: center;
}
.cp_ipselect select {
  width: 100%;
  padding-right: 1em;
  cursor: pointer;
  text-indent: 0.01px;
  text-overflow: ellipsis;
  border: none;
  outline: none;
  background: transparent;
  background-image: none;
  box-shadow: none;
  -webkit-appearance: none;
  appearance: none;
}
.cp_ipselect select::-ms-expand {
  display: none;
}
.cp_ipselect.cp_sl04 {
  position: relative;
  border-radius: 2px;
  border: 2px solid #da3c41;
  border-radius: 50px;
  background: #ffffff;
}
.cp_ipselect.cp_sl04::before {
  position: absolute;
  top: 0.8em;
  right: 0.8em;
  width: 0;
  height: 0;
  padding: 0;
  content: '';
  border-left: 6px solid transparent;
  border-right: 6px solid transparent;
  border-top: 6px solid #da3c41;
  pointer-events: none;
}
.cp_ipselect.cp_sl04 select {
  padding: 8px 38px 8px 8px;
  color: #da3c41;
}