From flutter/website#9183 (comment)

Currently the API docs does not distinguish which constructor should be used in what context.
The linked comment says:

We don't recommend using fromSwatch (M1/M2 concept) but rather fromSeed (M3+)

but the docs for fromSwatch say

This constructor is used by ThemeData to create its default color scheme.

• https://api.flutter.dev/flutter/material/ColorScheme/ColorScheme.fromSwatch.html

fromSeed is a bit clearer, but it isn't clear to me as a Flutter developer which I should use and how they differ in the context of M1/2 versus M3

Using the seedColor as a starting point, a set of tonal palettes are constructed. These tonal palettes are based on the Material 3 Color system and provide all the needed colors for a ColorScheme. These colors are designed to work well together and meet contrast requirements for accessibility.

• https://api.flutter.dev/flutter/material/ColorScheme/ColorScheme.fromSeed.html

While we're at it, the other constructors should be checked for the same clarity for M1/2/3:

• dark
• light
• highContrastDark
• highContrastLight