.collapsible3 {
  background-color: #f6f7f9;
  color: black;
  cursor: pointer;
  padding: 18px;
  width: 100%;
  border: none;
  text-align: left;
  outline: none;
  font-size: 15px;
}

.active, .collapsible3:hover {
  background-color:#ffffff;
 color: Black;
}

.content {
  padding: 0 18px;
  display: none;
  overflow: hidden;
  background-color: #f6f7f9;
}

<!--https://www.w3schools.com/howto/tryit.asp?filename=tryhow_js_collapsible -->