For getting the colon you need to define a new MakeIndex style; it's really simple: just prepare the following 31083.ist file in the same folder as your main document, with the single line
delim_0 ": "
because delim_0 is the container of the tokens inserted between an index entry and the first page number (if any). Then you have to instruct imakeidx to use the newly defined style.
For controlling the indentation of the following lines, you have to modify the definition of \@idxitem; something like
\makeatletter \renewcommand{\@idxitem}{\par\hangindent=20pt } \makeatother
will use 20pt instead of the default 40pt.
Complete example.
\documentclass{book} \usepackage{imakeidx} \makeindex[name=people,title=Index of People,options=-s 31083.ist -r] \makeatletter \renewcommand{\@idxitem}{\par\hangindent=20pt } \makeatother \begin{document} \mainmatter \chapter{Relativity} Einstein\index[people]{Einstein, Albert} Zorro\index[people]{Zorro} \newpage Einstein\index[people]{Einstein, Albert} Zorro\index[people]{Zorro} \newpage Einstein\index[people]{Einstein, Albert} Zorro\index[people]{Zorro} \newpage Einstein\index[people]{Einstein, Albert} Zorro\index[people]{Zorro} \newpage Einstein\index[people]{Einstein, Albert} Zorro\index[people]{Zorro} \newpage Einstein\index[people]{Einstein, Albert} Zorro\index[people]{Zorro} \newpage Einstein\index[people]{Einstein, Albert} Zorro\index[people]{Zorro} \newpage Einstein\index[people]{Einstein, Albert} Zorro\index[people]{Zorro} \printindex[people] \end{document}
I have used also the option -r to disable implicit range formation, otherwise the example would have shown "1–8" so not going to the second line. You'll probably want to remove it.
