To access your Moneydance preferences, choose File > Preferences.

On a Mac, choose Moneydance > Preferences.

This article details the options available within the "Appearance" tab.

ThemeChoose from multiple colour schemes, or select "customize" to create your own.
FontChoose your preferred font from the drop-down list.
Numeric FontAs above, the font that is used for numeric characters.
Printing FontThe font used when printing reports, graphs or cheques.
Font SizeSelect +1, +2 etc to increase the size, and choose -1, -2 etc to reduce from the default font size. 

If your appearance changes are not applied to the entire program, restart Moneydance.

Using older versions of Moneydance, you'll find the 'Theme' option within 'General' preferences