in PowerPoint 2002 and 2003 you can change font color
under custom animation. So, for example, if you have a
white background, you can design the text to change from
white (where it cannot be seen) to your desired color on
a click.
I guess that your question can be read several ways and will generate different
answers. For me it sounds like you want some special text to appear when the
mouse hovers over a bullet. In that case I would refer you to #16 at http://www.soniacoleman.com/Tutorials/PowerPoint/quicktricks.htm
