<li class="com" id="0" onClick="chosen(this)"><img src="images/com.png" class="iocn"></li>
<li class="com" id="1" onClick="chosen(this)"><img src="images/com.png" class="iocn"></li>
<li class="com" id="2" onClick="chosen(this)"><img src="images/com.png" class="iocn"></li>
<li class="com" id="3" onClick="chosen(this)"><img src="images/com.png" class="iocn"></li>
<li class="com" id="4" onClick="chosen(this)"><img src="images/com.png" class="iocn"></li>
function chosen(){
this.style.backgroundColor="blue";
}