function farbe() {
"use strict";
		const MY_ROW = document.getElementById("marks").getElementsByTagName("tr");
			for (let i in MY_ROW) {
				for (i=1; i <= MY_ROW.length; i = i + 2) {
					MY_ROW[i].style.backgroundColor = 'RED' ;
					}
				}
			}
		farbe();