style input number css

.number-wrapper {
  position: relative;
}

.number-wrapper:after,
.number-wrapper:before {
  position: absolute;
  right: 5px;
  width: 1.6em;
  height: .9em;
  font-size: 20px;
  pointer-events: none;
  background: #fff;
}

.number-wrapper:after {
  color: blue;
  content: "\25B2";
  margin-top: 1px;
}

.number-wrapper:before {
  color: red;
  content: "\25BC";
  margin-bottom: 5px;
  bottom: -.5em;
}