var trs=document.getElementsByTagName("tr");

for(var i=0;i<trs.length;i++){

       trs[i].setAttribute("onmouseover" ,"color(this)");

        trs[i].setAttribute("onmouseout" , "javascript:this.style.backgroundColor = 'blue'");

} 

function color(obj){

obj.style.backgroundColor = 'red';

}