Color increases visual impact dramatically, and one of the most effective uses of color is to emphasize selected text.
Select Complementary Colors to increase visibility, and avoid color clashes!
As a visual neuroscientist I'll also remind you that many folks experience some degree of color insensitivity (the most common form is a reduced sensitivity to reds and greens, in about 1 out of 10 males). If you use reds and greens, choose highly saturated colors instead of pastels, and use thicker lines (for instance, when showing different sets of data on a graph).
Be aware that, depending on the software you use, the film type, and the hardware used by whoever images your film, some colors you see on the computer screen will be changed in the final product. Another reason to plan ahead and finish the project ahead of time. You can then project the finished slides, and perhaps have time to re-work those inevitable ones which didn't work out the way you had planned.
You can REVIEW the Clarity, Font Styles, and Font Size pages, or RETURN to the 4 concepts page.