One of Flutter’s big strengths is its supports for theming;  you can define or change colours for every aspect of your UI but it can be a bit complicated. Now an open source project provides a way to simplify things. It’s called FlexColorScheme and is just superb.

The image shows the playground where you can pick a scheme and see how the controls look.

The documentation includes an indepth look at theming. The FlexColorScheme is a Flutter widget and there’s link to the source code on GitHub.  It is highly recommended.