Everyone thinks they like colorful slides, but the presentation creator needs to use color with discipline. The primary role of color is to highlight the differences in types of information. You may want to color one line of a text slide in red because you want to emphasize that point over all others. You may want to use different color bars on a bar graph to distinguish between the categories. Every color should have a purpose. It might be a minor point, but there should be a reason.
Don't decorate!!! Remember added bells and whistles divert the audience from the message your slide is meant to convey.
Below is a powerful use of color. The chart shows that the Ecology Division of the Mud Green Slime Production company doesn't share the Mud Green values. In fact the Ecology Division shares the environmental values of the outside environmental regulators that monitor the company's environmental performance . The slide also shows that the key to better environmental compliance is to "mix the shades of green," that is give the environmental office some training in "mud green" culture and give the other offices some environmental training.