how to change label from a form css code example

Example: how mto change the label font style in css

.swap {
  position: relative;
  padding-left: 80px;
}
.swap + .swap {
  margin-top: 5px;
}
.swap label {
  position: absolute;
  left: 0;
}

input:focus+label {
  font-family: 'Roboto Medium', sans-serif;
  font-size: 16px;
  color: #000;
  font-weight: 100;
}