Thanks for the sample files.
The JPEGs have three channels. But all channels contain have the exact same content. So, the image was converted to grayscale in your other app during processing.
So, that can’t be undone.
You can only use the colorize command inside GraphicConverter. But that will not give perfect results here. It is more designed for old photos.

- Bildschirmfoto 2026-07-05 um 18.35.23.jpg (161.28 KiB) Viewed 7467 times