Applying a White Color Fill to an Area
You will notice that if you attempt to fill an area in with a white
color the program will automatically switch it to black since white is not a
printable color. In some cases a white fill is helpful like when you are wanting
to block portions of a plot plan or create a background for text to be read
easily.
If you go to VIEW >> OPTIONS and uncheck Invert Pen and Invert
Pattern, your white areas will appear.