How to add aditional actions to argument into environement

Question

I am starting in LaTeX. I want to write a document and define some styles.

In this case I want to do two things with one portion of a paragraph:

1. That it has a red color
2. That it is aligned to the right

My problem is that I don't know how to do both when defining the environment.

This is my code:

%Define color
\newcommand{\txtred}[1]{\textcolor{red}{#1}}

%Command to use in the context
\newcommand{\atright}[1]{\renewcommand{\atright}{#1}}

\newenvironment{txtbook}
    {\begin{flushleft}}
        {\txtred{\atright}
    \end{flushleft}
}

In the context:

\begin{txtbook}Del libro del Génesis \hfill \atright{9, 8-15}\end{txtbook}

This works, but I want to translate \hfill to the environment, but I don't know how to do it.

I am using memoir, if there is some simpler way to do what I want I would appreciate it.

There is one example, at right, there is the argument:

Answer 1

If you really wish to use an environment and your current interface, the following will suffice:

\documentclass{memoir}

\usepackage{xcolor,lipsum}

\newcommand{\txtred}{\textcolor{red}}
\newcommand{\atright}{\mbox{}\hfill\txtred}
\newenvironment{txtbook}{%
  \raggedright
}{%
  \unskip\par
}

\begin{document}

\lipsum[1]

\begin{txtbook}
  Del libro del Génesis \atright{9, 8-15}
\end{txtbook}

\lipsum[2]

\end{document}

One can add some spacing adjustments, if needed.

Answer 2

I'd use a command, rather than an environment.

\documentclass{memoir}
\usepackage{xcolor}

\usepackage{lipsum} % for mock text

\newcommand{\txtbook}[2]{%
  \par\addvspace{\topsep}
  {\centering #1\hfill\textcolor{red}{#2}\par}\nopagebreak
  \addvspace{\topsep}
}

\begin{document}

\txtbook{Del libro del Génesis}{9, 8-15}

\lipsum[1]

\end{document}