Variable color for section titles

Question

The following def takes first three letters as an argument:

\newcounter{colorCounter}
\def\@sectioncolor#1#2#3{%
  {%
    \color{%
      \ifcase\value{colorCounter}%
        blue\or%
        red\or%
        orange\or%
        green\or%
        purple\or%
        brown\else%
        headercolor\fi%
    } #1#2#3%
  }%
  \stepcounter{colorCounter}%
}

It actually colors first three letters of the section name. How do I make it color the whole section name instead?

Can I make it to take the whole paragraph as an argument?

Edit

In order to make it work one has also to

\renewcommand{\section}[1]{
  \par\vspace{\parskip}
  {%
    \LARGE\headingfont\color{headercolor}%
    \@sectioncolor #1%
  }
  \par\vspace{\parskip}
}

Edit 2

MWE:

\documentclass{article}

\usepackage{fontspec}
\usepackage{polyglossia}

% fonts:
\defaultfontfeatures{Scale=MatchLowercase,Mapping=tex-text}
\setmainfont{DejaVu Sans}
\setsansfont{DejaVu Sans}
\setmonofont{DejaVu Sans Mono}

\usepackage{xcolor}
\colorlet{headercolor}{gray}

\newcounter{colorCounter}
\def\@sectioncolor#1#2#3{%
  {%
    \color{%
      \ifcase\value{colorCounter}%
        blue\or%
        red\or%
        orange\or%
        green\or%
        purple\or%
        brown\else%
        headercolor\fi%
    } #1#2#3%
  }%
  \stepcounter{colorCounter}%
}

\renewcommand{\section}[1]{
  \par\vspace{\parskip}
  {%
    \LARGE\color{headercolor}%
    \@sectioncolor #1%
  }
  \par\vspace{\parskip}
}

\begin{document}


\section{aaaaaa}

\section{bbbbbb}

\section{cccccc}

\end{document}

Answer 1

Use sectsty (or, with some more work, titlesec):

\documentclass{article}

\usepackage{fontspec}
\usepackage{xcolor}
\usepackage{sectsty}

\colorlet{headercolor}{gray}

\newcounter{colorCounter}
\newcommand\sectioncolor{%
    \color{%
      \ifcase\value{colorCounter}%
        blue\or
        red\or
        orange\or
        green\or
        purple\or
        brown\else
        headercolor\fi
  }%
  \stepcounter{colorCounter}%
  % Remove the following line if you don't want to cycle
  \ifnum\value{colorCounter}=7 \setcounter{colorCounter}{0}\fi
}

% in section titles \sectioncolor will be executed
\sectionfont{\sectioncolor}

% don't number sections
\setcounter{secnumdepth}{0}

\begin{document}

\section{aaaaaa}

\section{bbbbbb}

\section{cccccc}

\section{dddddd}

\section{eeeeee}

\section{ffffff}

\section{gggggg}

\section{hhhhhh}

\end{document}

Answer 2

Oh I solved it:

\documentclass{article}

\usepackage{fontspec}
\usepackage{polyglossia}

% fonts:
\defaultfontfeatures{Scale=MatchLowercase,Mapping=tex-text}
\setmainfont{DejaVu Sans}
\setsansfont{DejaVu Sans}
\setmonofont{DejaVu Sans Mono}

\usepackage{xcolor}
\colorlet{headercolor}{gray}

\newcounter{ColorCounter}
\newcommand\Color{
  \color{%
    \ifcase\value{ColorCounter}%
      blue\or%
      red\or%
      orange\or%
      green\or%
      purple\or%
      brown\else%
      headercolor%
    \fi%
  }
}

\renewcommand{\section}[1]{
  \par\vspace{\parskip}
  {
    \LARGE\Color #1
  }
  \par\vspace{\parskip}
  \stepcounter{ColorCounter}
}

\begin{document}


\section{aaaaaa}

\section{bbbbbb}

\section{cccccc}

\end{document}