Color and Material Design Palette.

Encourages app develpers to embrace the use of color not just for aesthetics but to make your app easier to use.

Using Color

Primary Color - Represents your apps branding. Its applied on the toolbar making the app instantly recognizable.

Accent Color- Brighter more saturated color that is used to draw attention to certain elements such as FAB.

If you have primary color and primary color dark but no accent color, then you can use complementary colors to help you get one. Check color.adobe.com