These captures are from 2016, but 2013 should be substantially similar.
Look in the Page Layout tab > Themes drop down a grid of themes is displayed. Your first example appears to be using a custom Light style in the default "Office" theme
I suspect that you will see that a different theme is selected, "highlighted" in each workbook.
The first one looks like the default "Office" theme, with an additional, "custom" light colored table style <edit
theme>. Here is what mine looks like:
I haven't bothered to look, but if you look carefully at your second screen cap you'll see a substantially different set of options.