Colored text with dcolumn

Question

I want to typeset a table where certain numbers are going to appear red. In order to achieve the correct alignment I am using the dcolumn package. The problem is that the parsing that dcolumn does, prevents the correct appliance of color.

In the following example, in the third row, only the "1" appears red. The dot and the "32" appears black. Using \textcolor results in a syntactical mistake.

I tried using siunitx, but unfortunately, since I am producing programmatically hundreds of tables, the compilation time increased too much (more than a minute)

So the question is, how can you color a number belonging in a dcolumn?

\documentclass[]{article}

\usepackage{xcolor}
\usepackage{tabu}
\usepackage{dcolumn}

\newcolumntype{d}[1]{D{.}{.}{#1}}

\begin{document}

\begin{tabu}{cd{2}}
note & 1.32\\
\color{red}note & 1.32 \\
\color{red}note & \color{red}1.32 \\
% note & 1.32\\
% \textcolor{red}{note} & 1.32 \\
% \textcolor{red}{note} & \textcolor{red}{1.32} \\  % results in a compilation error.
\end{tabu}

\end{document}

Answer 1

I can provide an approach by redefining the internal definition of the output.

The contents of a dcolumn is saved in two boxes and so you have to set the color before the output. Additional you must reset the color.

The example below provides a new command \dcolcolor to set the color of a cell defined by dcolumn. The usage is simple (\dcolcolor has one mandatory argument):

\dcolcolor{<color>}

Here the example:

\documentclass[]{article}

\usepackage{xcolor}
\usepackage{tabu}
\usepackage{dcolumn}

\newcolumntype{d}[1]{D{.}{.}{#1}}
\makeatletter
\def\DC@endright{$\hfil\egroup\@dcolcolor\box\z@\box\tw@\dcolreset}
\def\dcolcolor#1{\gdef\@dcolcolor{\color{#1}}}
\def\dcolreset{\dcolcolor{black}}
\dcolcolor{black}
\makeatother
\begin{document}

\begin{tabu}{cd{2}}
note & 1.32\\
\color{red}note & 1.32 \\
note &\dcolcolor{red} 1.32 \\
 note & 1.32\\
 note & \dcolcolor{red}1.32\\
 \textcolor{red}{note} & 1.32 \\
\end{tabu}
\end{document}

Answer 2

You may want to also check out the formatting capabilities of the siunitx package. The package provides, among many other things, a column type labeled S. With this package loaded instead of dcolumn, your MWE would like this this:

\documentclass[]{article}
\usepackage{xcolor}
\usepackage{tabu}
\usepackage{siunitx}

\begin{document}
\begin{tabu}{cS[table-format=1.2]}
note & 1.32\\
\color{red}note & 1.32 \\
\color{red}note & \color{red}1.32 \\
\textcolor{red}{note} & 1.32 \\
\textcolor{red}{note} & \textcolor{red}{1.32} \\
\end{tabu}
\end{document}

Observe that the package and its S column type have no problems with either \color or \textcolor.