Change the Font Color, Size, and Style in Diagrams (Visual Database Tools)
You can customize the way text appears in database diagrams by changing the font color, size, and style. The changes are applied to new diagrams and to existing diagrams when they are modified.
To change the font color, size, and style in diagrams
On the Tools menu, click Options.
Expand Environment, and then click Fonts and Colors.
In the Show settings for list, select Table and Database Designers.
Change the font, size, display item, foreground and background colors.