Well in the code that you use to loop through the headlines, you have to setup a flag variable where if the flag is true, print it with one color, then set the flag to false... if the flag is false, print it the other color and set the flag to true.
That way as you go through the loop the flag is going true, false, true, false and printing each headline background with a different color.
If you are not using a programming language to print the headlines, then you will have to just do it manually for each cell you want to change colors or mark each cell with a different CSS class like one called "color1" and another called "color2" and then manually add the class designation to every cell, switching both back and forth.
But if you are printing with a language like PHP, ASP, or ColdFusion the flag approach would be the easiest and fastest.
Hope that makes some sense.