Keep colourisation out of the evidence
Do not colourise an old photograph to guess what the original scene looked like. Generated colours are interpretations. They can change the visual signals sent to a search engine and make later comparison harder.
Compare structural details
- Preserve the monochrome file unchanged.
- Search the complete composition.
- Try a crop around a distinctive non-personal feature if needed.
- Compare shapes, shadows and object positions on candidate source pages.
For example, a monochrome portrait reused from a colour publicity photograph may retain the same fold in a sleeve and the same background geometry. Those features are more informative than a general resemblance between faces.
Record the transformation carefully
If you find a likely colour source, keep both URLs and explain why you think they are versions of the same image. Do not describe the colour copy as original solely because it is in colour. A publisher may have created both variants, and a larger file may still be a later derivative. Publication records or the creator's own archive provide better context.
Continue with photo formats and metadata.