History of Field::colour 1 change

In crates/backdrop/src/field.rs, lines 129–144 on v0.9.21. Every change that wrote or deleted one of these lines, or deleted a line from between them. Exact, because each line keeps its identity across edits; edits elsewhere in the file are not here. Also: oxy log -L 129,144:crates/backdrop/src/field.rs.