Color schemes are associated with the slide-title master pair. Every master pair has at least one color scheme, but most have several (up to 16). You can modify existing color schemes to create new color schemes.
You can apply any one of the available, standard color schemes to the master.
When you create a slide, it inherits the color scheme applied to its master. On a slide, you can apply one of the other available standard color schemes and thereby override the color scheme of the master.
Each object you create on a slide inherits its color from the appropriate element in the slide's color scheme. You can change the color of an object and override the color that comes from the color scheme.
You can also change the color of an object or placeholder on the master. For example, you could modify the color of second-level bullets on the slide master. In this event, second-level bullets on a slide based on that master will use the color defined on the master.