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The colors to use to paint the logo. This map should contain at least two values, one for 400 and one for 900.
If possible, the default should be used. It corresponds to the
Colors.blue swatch from the Material library.
If for some reason that color scheme is impractical, the Colors.amber,
Colors.red, or Colors.indigo swatches can be used. These are Flutter's
secondary colors.
In extreme cases where none of those four color schemes will work,
Colors.pink, Colors.purple, or Colors.cyan swatches can be used.
These are Flutter's tertiary colors.