Edit in JSFiddle

    $(".box").click(function () {
        $(".box").toggleClass("change_color");
    })

	<div class="box">
		<p>please, click here!</p>
	</div>

		.box {
			max-width:960px;
			margin: 0 auto;
			height:500px;
			background-color: #009ac8;
		}
		.box p{
			padding-top:22%;
			color: #fff;
			text-align: center;
			font-size: 5em;
		}
		.change_color {
			background-color: #ff3494;
		}