Am using TeX Live 2012, pdflatex, and latexmk to produce the document, on Ubuntu Linux.
In the following image, Okular is shown on the left and Adobe Acrobat Reader is shown on the right.
The images in the document most likely contain various colour spaces. The colours in Okular are desired (and shown as coded in the LaTeX); whereas, the colours in Acrobat Reader are not desired.
I have read a few different questions on this topic, including:
What is most likely the problem with the colours in Adobe Acrobat Reader, and how should I resolve it?
I was thinking that the problem might be caused by having images in multiple color spaces. If that's the case, then I could resolve it by running the images through ImageMagick.
The alternative is to use
xcolor, as suggested.