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I am a publisher who works with PDFs that authors submit that were created from LaTex. Often the PDF is in color and the author can't fix this issue. Has anyone had this issue and is there a quick fix I can point our authors too?

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    What do you mean by colour that shouldn't be there? Do you want to convert the PDF to a black and white copy or are there specific colourings appearing which you can give examples of? – Dai Bowen Nov 1 '16 at 13:27
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You could remove \usepackage{xcolor} or \usepackage{color} from the preamble, and see what breaks. But the chances are that loading colour-support is actually done by the graphicx package (manual). This package supports an option monochrome which should do what you want. To apply this option just change \usepackage{graphicx} to

\usepackage[monochrome]{color}
\usepackage{graphicx}

The colour model used is unlikely to be the issue as a simple

\documentclass{article}
\begin{document}
Hello world
\end{document}

is in the sRGB colour space according to identify (ImageMagick):

test.pdf PDF 595x842 595x842+0+0 16-bit sRGB 1.503MB 0.000u 0:00.002

in fact even with \usepackage[cmyk]{xcolor} we still get sRGB according to ImageMagick. This is all on Tex Live 2015/Windows.

As the expert (David Carlisle) pointed out in a comment below, none of this will deal with colour in images. Some images may look monochrome but actually have colour components (scans for example). In an answer to a related question I linked to a script that finds colour pages in a pdf by comparing the RGB channels of each pixel. This may help you track down the offending pages, and hopefully the offending figures (if they are the issue).

For simply forcing pdfs to monochrome or greyscale, they are some suggestions at superuser, but they would need to be used with care.

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    the usual problem for printers is that the color model used in a pdf file is rgb, whereas print (for traditional presses) requires cmyk. the manual isn't specific about whether [monochrome] applies cmyk; if it doesn't, there could still be problems. do you happen to know which color model is applied when the [monochrome] option is specified? – barbara beeton Nov 1 '16 at 13:38
  • @barbarabeeton I don't, but given that this isn't a universal problem just disabling colour ought to be enough. I'll have a dig – Chris H Nov 1 '16 at 13:44
  • @barbarabeeton I've put some more info in the answer – Chris H Nov 1 '16 at 14:06
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    @barbarabeeton monochrome disables colour completely all colour specials just write to the log and you get black and white only. Of course if images are in colour, they stay coloured. – David Carlisle Nov 1 '16 at 20:42
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    For converting the pdf to greyscale, there's jmakepdfx which is just a Java GUI that uses ghostscript. (It also converts to PDF/X.) It's worked fine (so far) for me for all the times I've had to convert a pdf produced by LaTeX into a print-ready greyscale version. – Nicola Talbot Nov 2 '16 at 11:58

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