There are dozens of ways to overlay text onto a potentially confusing background. A subtle yet effective technique can be to add a “drop shadow” to the text. That is simply a software-added effect that makes it appear that there is a light source casting a shadow from one element (the text) onto another (the background).
In PowerPoint there is a simple command in the font menu that will accomplish this. However this is usually not strong enough and the parameters of the effect must be tweaked to create maximum legibility.
It may not always work, but your first attempt might be to use a shadow to separate confusing elements. Just make sure to judge the overall effectiveness from the audience’s point of view.
