A theme is the set of colors that will be applied to the Angular Material components. The library's approach to theming is based on the guidance from the Material Design spec. In Angular Material, a theme is created by composing multiple palettes. In particular, a theme consists of: A primary palette: colors most widely used across all screens and components. An accent palette: colors used for the floating action button and interactive elements. A warn palette: colors used to convey error state. A foreground palette: colors for text and icons. A background palette: colors used for element backgrounds