5

This question is about the use of colors in professional printing.

I made the following table:

\documentclass{article}
\usepackage{xcolor}
\usepackage{colortbl}
\definecolor{rga}{HTML}{00E516}   % red-green gradient
\definecolor{rgx}{HTML}{19E700}
\definecolor{rgc}{HTML}{4AEA00}
\definecolor{rgd}{HTML}{7DEC00}
\definecolor{rge}{HTML}{B1EF00}
\definecolor{rgf}{HTML}{E5F200}
\definecolor{rgg}{HTML}{F4CD00}
\definecolor{rgh}{HTML}{F79B00}
\definecolor{rgi}{HTML}{F96800}
\definecolor{rgj}{HTML}{FC3500}
\definecolor{rgk}{HTML}{FF0000}

\begin{document}
\begin{tabular}{|cccccccc|}
\hline
$\Delta$ & $E_2$ & $P_1$ & $P_2$ & $P_3$ & $P_4$ & $P_5$ & $P_6$\\
$E_1$ & \cellcolor{rgj}11.18 & \cellcolor{rgi}10.66 & \cellcolor{rgj}11.23 & \cellcolor{rgh}9.90 & \cellcolor{rgj}11.39 & \cellcolor{rgi}10.72 & \cellcolor{rgh}10.26\\
$E_2$ & & \cellcolor{rgi}10.72 & \cellcolor{rgj}11.15 & \cellcolor{rgi}10.49 & \cellcolor{rgk}12.29 & \cellcolor{rgk}12.12 & \cellcolor{rgk}11.98\\
$P_1$ & & & \cellcolor{rgh}10.19 & \cellcolor{rgf}8.71 & \cellcolor{rgi}10.61 & \cellcolor{rgf}8.97 & \cellcolor{rge}8.47\\
$P_2$ & & & & \cellcolor{rgf}9.08 & \cellcolor{rgi}10.41 & \cellcolor{rgg}9.70 & \cellcolor{rgi}10.63\\
$P_3$ & & & & & \cellcolor{rge}8.22 & \cellcolor{rgd}7.70 & \cellcolor{rge}8.23\\
$P_4$ & & & & & & \cellcolor{rga}6.00 & \cellcolor{rgf}8.60\\
$P_5$ & & & & & & & \cellcolor{rgx}6.55\\
\hline
\end{tabular}
\end{document}

The pdf looks like this:

enter image description here

I could have probably automated the cell coloring, but this question is not about that.

It was printed on a conference poster, as follows:

enter image description here

I realize that using RGB colors was a bad idea, and that I should have used CMYK. However, I would expect some minor shifts (as in, e.g., Option cmyk for xcolor package does not produce a CMYK PDF), not that green would turn into blue.

The question is: is this amount of color difference common, or is this the result of some strange conversion by the print shop? Other colors on the poster (font colors, images) looked ok. Note that I can't ask them myself, because the conference offered free printing and I collected the poster at the conference registration desk. However, I would like to know if I can expect this again, and if yes, how to avoid it.

  • I wouldn't blame the RGB colors, the sRGB colorspace is standard and can be handled by every professional printer. The colors in your picture are reeeally far off and I'd blame the printing of the conference. To be sure you need the color profile of the printer to make a softproof. For normal paper I feel its not really necessary (when professional printers are used), but for other materials like canvas or metal (printing of photos for galleries), there are huge differences depending on the material. – thewaywewalk Aug 19 '16 at 8:56
5

As far as I know, the only reliable way to obtain exactly what you want on printing is to use the PANTONE colorspace, to which you have access through the spotcolorpackage under pdflatex, or xespotcolor under xelatex.

Here is a link to a Pantone colours palette.

3

If you stick to pdftex or luatex (ie, not xetex), an alternative package is colorspace, which is simpler and more complete than spotcolor (caveat: I'm its author). It supports shades (ie, spot + black) and mixed spot colors, as well as ICC profiles for the default CMYK, RGB and Gray spaces (which is what I think you are looking for). It also supports the ! notation.

For example, for a spot color after loading the package just say something like:

\definespotcolor{mygreen}{PANTONE 7716 C}{.83, 0, .40, .11}

Then you can say \color{mygreen!60}. It also handles the internal PDF color spaces better than spotcolor.

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