Product and version
FileMaker Pro 15, FileMaker Pro 16
OS and version
The new PDF engine incorrectly handles certain RGB color profiles, showing a muddier version of the image. The color profiles I know to be affected are Adobe RGB (1998) and ProPhoto RGB.
The old PDF engine correctly handled these images.
How to replicate
1) Include either of the two attached images in a record
2) Save the record to PDF
In photoshop, change to a different RGB color profile. This is not practical when many images are affected