Changing fonts

In Visualization module, from the main menu bar, select Viewport > Viewport Annotations Options…

Go to the Legend tab. Now, click on the Set Font… button and this will bring up the Select Font form. Tick the Legend box to change the text size of the contour legends. Click on OK in this form.

Additionally, see this article (Section 1. Changing Fonts):

A Fast Guide to the Most Useful Tasks in Abaqus Visualization Module (PART A)

 However, doing this process each time is rather annoying. To set the font size to a larger size (as you like) automatically, each time Abaqus opens, follow the instruction in:

Q&A 119: How can I save graphical settings I made in Abaqus/CAE? I do not want repeat these settings when opening Abaqus again.