In your Work Environment>User Preferences>On screen Preferences> there is a setting for "Automatic Pen Color Adjustment". This is an on-screen option for items of the same color to show differently on the screen, but does NOT print. It makes working easier. So, as in your example white on white the text background shows slightly grayed for visual feedback.
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"