I don't like default theme (colors and fonts) in Office. I really like the style of the new Microsoft blog posts (title and body font is Segoe UI). Here's an example of what a Microsoft blog post looks like.
I used to manually change the fonts in Word - and I had to remember to do so each time I added new text to the document since the default fonts Calibri for the body text and Cambria Light for headings. Now, I use a custom theme to quickly change the fonts and the color scheme for in my documents. Once I apply the custom theme, any changes I make to the document follow the font selections from the theme.
Here's how to create a custom theme and make it easily accessible in Word: