I am using Illustrator to prepare some scientific figures. The figure has a number of "placed" (File -> Place...) panels. When I "embed" some of these panels, then export the figure to PDF, the colours of the embedded and non-embedded panels will appear different in all PDF readers. The magnitude of the difference is not the same in Mac Preview and Acrobat though. And within Illustrator the colours are the same.
Why does this happen and how can I avoid this apparent colour change?
I do not need accurate colour but I do need consistency.