#ca1{border:1px solid black;}

.button {
  width: 72px;
  border-radius: 8px;
  transition-duration: 0.4s;
}

.button1:hover {
	background-color: red;
}

.button2:hover {
  background-color: blue;
}

.button3:hover {
  background-color: black;
  color: white;
}

.button4:hover {
  background-color: white;
}