On page one of this tutorial, I mentioned that it is important to have good contrast on your slides, between the background color and the text color. OpenOffice Impress has a neat feature that automatically changes the text color (if necessary) to a selection that is optimal for reading the text, when you choose a different background color. However, any changes you have made manually yourself, by selecting a specific color for the text will not be affected by this automation.
In the screenshots above, note the changes on the white slide, that I made earlier in this tutorial. The title is black (original color), and I changed the bulleted text manually, to green.
The second screenshot shows the newly changed background color I have applied to the slide -- dark blue. Since I had made no color change to the title text, OpenOffice Impress automatically sensed that black would be a poor color choice for this background and changed it to white. The green bulleted text remained, since I had made that change manually.