CSS

change bg color on hover

/* Change background color on hover */
.myClass:hover {
  background-color: yellow;
}

hover bg change

<style>
.mydivouter{
	position:relative;
	background: #f90;
    width: 200px;
    height: 120px;
    margin: 0 auto;
}
.mydivoverlap{
    position: relative;
    z-index: 1;
}
.mybuttonoverlap{
	position: absolute;
    z-index: 2;
    top: 44px;
    display: none;
    left: 59px;	
}
.mydivouter:hover .mybuttonoverlap{ 
	display:block;
}
</style>
<div class="mydivouter">	
	<button type="button" class="mybuttonoverlap btn btn-info">Read More</button>
</div>