I just discovered how to change fonts and add colors to Notes by using command T. How can I change fonts and add colors to Contacts? (Conmmand T does not work for Contacts).
The Contacts app uses the system font. To change font or font size in Contacts.app, you must change it for your whole system. There is a way to change the system font from San Francisco font to Lucida Grande font which may be more appealing to you. There is a small app that lets you pick between San Francisco and Lucida Grande fonts for your system. This web page provides a link to the application or you can go straight to it here.