Recent newsgroup question, "How do I get white text over a black background?" Like this:
Use a filled region to create the black background then edit your text/labels.
[True for 2009 and previous]
Amended for for 2010
Color: RGB 251,251,251 (nearly white, RGB 254,254,254 is displayed "black")
Caution if you export sheet views to dwg you'll need to adjust your pen table to plot the text correctly. If you assign the text on the titleblock to its own layer you can tell AutoCAD to plot them using the object color so the text will plot over the background hatch. There are probably other options as well.