<ul>
  <li class="a">Put on!</li>
</ul>

li {
	display : inline-block;
	background: #74653D; 
	color: #FFFBD5; 
	width: 300px;
	line-height: 66px;
	text-align: center;
  font-size: 28px;
  font-weight: bold;
	margin-right: 20px;
	-webkit-transition: all 0.5s;
	transition: all 0.5s;
}
.a:hover {
  opacity: 0.7; /*背景と文字色の透明度が変わる*/
}