[surye]

The "diff" appears to be backwards (it's subtracting what prettier would emit, and adding back the original).

[ematipico]

The red represents what would Prettier emits, and the green represents what Biom e emits. If you think that's unclear, feel free to send a PR to help us make it clearer.

[globular-toast]

This was intuitive to me, especially because it's in a section titled "Differences with Prettier".

[explaininjs]

The diff is between the test cases’s expected output (red) and the utility’s current output (green).