Orange diagonal with outer numbers
I really like this version. For one thing, orange and gray are a great combination, but more importantly it has an other-worldly weirdness that I very much appreciate it. I guess the strangeness comes from being a novel (I think) way to extend everyday two-dimensional tables with one extra dimension. It's not a perfect extension--confusing and difficult to follow--but it's intriguing. (Check this version to see how it works.)
Unfortunately, it takes way too much space. Which was why I tried, with mixed success, to move the numbers inside the diagonals.