Vanessa asks,
@srikat Is it possible to make the border colors alternate for posts in Genesis?
We can add odd/even post class for Posts alternately and use these in CSS.
Adding the following in child theme's functions.php will add 'odd' class to 1st (top most), 3rd, 5th.. and 'even' class to 2nd, 4th, 6th.. in Posts page, Archives and Search results.
Depending on how old the web browsers are you have to support, you can also do this in CSS alone, if I’m not mistaken, by using the :nth-child, or :nth-of-type pseudo selectors so there isn’t any PHP code needed.