One single colored letter inside \spacedallcaps

Question

I want to change the color of a single letter inside a custom \spacedallcaps command. This command makes the specified text uppercase and changes the letter spacing.

When I introduce a \textcolor{color}{letter} it will simply not work.

Also, taking the letter out of the \spacedallcaps piece of text works only if the specified letter is at the end or at the beginning. But how can I manage this when the letter is in the middle of a word?

I tried the following :

\documentclass{article}
\usepackage{color}
\usepackage{textcase} % for \MakeTextUppercase
\usepackage{soul} % for letterspacing
\sodef\allcapsspacing{\upshape}{0.25em}{0.8em}{0.6em} % : {space between letters}{space between words}{0.6em}
\DeclareRobustCommand{\spacedallcaps}[1]{\MakeTextUppercase{\allcapsspacing{#1}}} % all caps with better spacing

\begin{document}
\spacedallcaps{One single colored letter}\\

\spacedallcaps{One single col}\hspace{0.25em}\textcolor{red}{O}\spacedallcaps{red letter}\\

\spacedallcaps{One single col}\hspace{0.25em}\textcolor{red}{O}\hspace{0.25em}\spacedallcaps{red letter}
\end{document}

But the result is far from being good :

One can always play with the \hspace function but it is extremely tedious as it requires endless trials.

How can one achieve this automatically?

Answer 1

Use xcolor instead of color and issue

\colorlet{RED}{red}

because \MakeTextUppercase also "uppercases" red inside \textcolor.

At this point (notice \textcolor inside braces)

\spacedallcaps{One single col{\textcolor{red}{O}}red letter}

would suffice.

MWE

\documentclass{article}
\usepackage{xcolor}
\usepackage{textcase} % for \MakeTextUppercase
\usepackage{soul} % for letterspacing
\sodef\allcapsspacing{\upshape}{0.25em}{0.8em}{0.6em} % : {space between letters}{space between words}{0.6em}
\DeclareRobustCommand{\spacedallcaps}[1]{\MakeTextUppercase{\allcapsspacing{#1}}} % all caps with better spacing

\colorlet{RED}{red}

\begin{document}
\spacedallcaps{One single col{\textcolor{red}{O}}red letter}
\end{document} 

Output

---

I would like to add a suggestion from Christopher for adjusting the spacing between letters.

\documentclass{article}
\usepackage{xcolor}
\usepackage[letterspace=150]{microtype}

\DeclareRobustCommand{\spacedallcaps}[1]{\MakeUppercase{\textsc{#1}}} % all caps with better spacing

\colorlet{RED}{red}

\begin{document}

\spacedallcaps{\lsstyle One single col\textcolor{red}{O}red letter}

\end{document} 

Answer 2

You can register commands for soul:

\documentclass{article}
\usepackage{color}
\usepackage{textcase} % for \MakeTextUppercase
\usepackage{soul} % for letterspacing
\sodef\allcapsspacing{\upshape}{0.25em}{0.8em}{0.6em} % : {space between letters}{space between words}{0.6em}
\DeclareRobustCommand{\spacedallcaps}[1]{%
  \MakeTextUppercase{\allcapsspacing{#1}}%
} % all caps with better spacing

\DeclareRobustCommand{\makered}[1]{\textcolor{red}{#1}}
\soulregister{\makered}{1}

\begin{document}
\spacedallcaps{One single col{\makered{o}}red letter}
\end{document}

Answer 3

Just wanted to see if this would work with my \spaceout macro, not using soul.

EDITED to provide for separate inter-word spacing.

Provides definitions \theLetterSpace and \theWordSpace as default inter-letter and inter-word spacing (Note that \theWordSpace is in addition to the natural \ space that accompanies word breaks). By default, I set \theWordSpace to 1.5 x the local letter-spacing, dynamically readjusted as \theLetterSpace changes. The local value of the letter spacing can also be changed with an optional argument to \spaceout, as shown in the MWE.

\documentclass{article}
\usepackage{xcolor}
\def\theLetterSpace{0.5pt}
\def\theWordSpace{1.5\LocalLetterSpace}
\newlength\LocalLetterSpace
\newcommand\spaceout[2][\theLetterSpace]{%
  \setlength\LocalLetterSpace{#1}\expandafter\spaceouthelpA#2 \relax\relax}
\def\spaceouthelpA#1 #2\relax{%
  \spaceouthelpB#1\relax\relax%
  \ifx\relax#2\else\ \kern\theWordSpace\spaceouthelpA#2\relax\fi
}
\def\spaceouthelpB#1#2\relax{%
  #1%
  \ifx\relax#2\else
    \kern\LocalLetterSpace\spaceouthelpB#2\relax%
  \fi
}
\parskip 1ex
\colorlet{RED}{red}
\begin{document}
test \uppercase{\spaceout[5pt]{one single col{\textcolor{red}{o}}red letter}} with 5pt added spacing

test \uppercase{\spaceout[3pt]{one single col{\textcolor{red}{o}}red letter}} with  3pt added spacing

test \uppercase{\spaceout[1pt]{one single col{\textcolor{red}{o}}red letter}} with  1pt added spacing

\def\theWordSpace{5\LocalLetterSpace}Change the inter-word spacing to 5 x local letter spacing.

test \uppercase{\spaceout[1pt]{one single col{\textcolor{red}{o}}red letter}} with  1pt added spacing
\end{document}