body{
	font-family: sans-serif;
	background-color: lightblue;
<!--	background-image: url("http://gym-pefkon.thess.sch.gr/images/sky.jpg");  -->


}
h1{
	text-align: center;
	color: forestgreen;
	margin: 30px 0 50px;
}
.gallery{
	margin: 10px 50px;
}
.gallery img{
	width: 200px;
	padding: 5px;
<!--	filter: grayscale(100%); -->
	transition: 1s;
}
.gallery img: hover{
	filter: grayscale(0);
	transform: scale(1.1);
}