Bad colors in table using baposter

I'm trying to assign specific colors to table cells in a poster (baposter). Unfortunately they are reproduced much to dark in the pdf. As they have to match the colors of my graphs I definitely need the original ones. In my presentation (beamer) the colors are reproducing nicely. Therefore I assume the table and use of \cellcolor is fine.

Please find a working example below:

\documentclass[a0paper,portrait]{baposter}
\usepackage{relsize} % Used for making text smaller in some places
\usepackage{color, colortbl}  % define own fancy colours
\graphicspath{{figures/}} % Directory in which figures are stored

\definecolor{VeryCold}{HTML}{000000}  % becomes 231F20 in the pdf
\definecolor{Cold}{HTML}{FFFFFF}  % stays FFFFFF in the pdf
\definecolor{Cool}{HTML}{FF0000}  % becomes ED1C24 in the pdf
\definecolor{SlightlyCool}{HTML}{00FF00}  % becomes 00A650 in the pdf
\definecolor{Comfortable}{HTML}{0000FF}  % becomes 2E3192 in the pdf
%\definecolor{Comfortable}{RGB}{00, 00, 255}  % no difference so the method to define the colors should be fine


\begin{document}

\background{ % Set the background to an image (background.pdf)
\begin{tikzpicture}[remember picture,overlay]
\draw (current page.north west)+(-2em,2em) node[anchor=north west]
%{\includegraphics[height=0.0852\textheight, width=0.9842\textwidth]{backgroundBlau}};  % 0.968
{ };
\end{tikzpicture}
}

\begin{poster}{
grid=false,
borderColor=Cold, % Border color of content boxes
headerColorOne=Cold, % Background color for the header in the content boxes (left side)
headerColorTwo=Cold, % Background color for the header in the content boxes (right side)
headerFontColor=Comfortable, % Text color for the header text in the content boxes
boxColorOne=white, % Background color for the content in the content boxes
headerfont=\Large\sf\bf, % Font modifiers for the text in the content box headers
textborder=rectangle,
background=user,
headerborder=open, % Change to closed for a line under the content box headers
boxshade=plain
}
{}
%
{\sf\bf \textsmaller[1]{\textcolor{white}{ text }}} % Poster title
{\vspace{0.1em} text \\ % Author names
{\smaller text }} % Author email addresses
%{\includegraphics[scale=0.55]{Uni_Logo-Grundversion_E1_A4_CMYK}} % University/lab logo

\headerbox{Introduction}{name=introduction,column=0,row=0}{

\textsmaller[1]{
\begin{center}
\begin{tabular}{|c|c|c|c|}
\hline
\rowcolor{Comfortable}\multicolumn{1}{|c|}{PET} & \multicolumn{1}{|c|}{eption} & \multicolumn{1}{|c|}{ Stress} & \multicolumn{1}{|c|}{Color} \\ \hline \hline
< 4 & ld & ress & \cellcolor{VeryCold}\\ \hline
4 - 8 & old & sts & \cellcolor{Cold} \\ \hline
8 - 13 & ol &  ss & \cellcolor{Cool} \\ \hline
13 - 18 & ool & s & \cellcolor{SlightlyCool} \\ \hline
18 - 23 & e & st & \cellcolor{Comfortable} \\ \hline
\hline
\end{tabular} 
\end{center}
}

}

\end{poster}
\end{document}

The colors in the example should be black, white, red, green, blue. While black and white seem to be fine, red green and blue are way to dark.

Any idea is highly appreciated!