"ProPhoto" > "Customize" > "Proofing Appearance" > "General"
The user toolbar is the area directly above the left hand corner of the proofing gallery thumbnail page display.
Using this option area, you can modify the text appearance of the user toolbar area. Our General Text Appearance Overview tutorial explains what each of the individual text appearance settings does.
Just be aware that any settings you make in this area may also affect the Log In/Log Out button as well, if no specific settings are made in the “Text buttons appearance” are. So for example, if in the “Text buttons appearance” area no font is selected, but you do select a font in this “User Toolbar Text Appearance” area, it will be applied to the Log In/Log Out button.