\begin{tikzpicture}
  \begin{axis}[
      xmin=0, xmax=6.5, ymin=0, ymax=40,
      width=9cm, height=6cm,
      xlabel={r [nm]}, ylabel={g(r)}]
    \addplot[mark=none,orange] table[comment chars={@,\#}, x index=0, y index=1] {\relativepath rdf_550ns-700ns.xvg};
    \addlegendentry{CO}
    \addplot[mark=none,green] table[comment chars={@,\#}, x index=0, y index=2] {\relativepath rdf_550ns-700ns.xvg};
    \addlegendentry{POPC}
    \addplot[mark=none,magenta] table[comment chars={@,\#}, x index=0, y index=3] {\relativepath rdf_550ns-700ns.xvg};
    \addlegendentry{apoA-I}
    \addplot[mark=none,red] table[comment chars={@,\#}, x index=0, y index=4] {\relativepath rdf_550ns-700ns.xvg};
    \addlegendentry{NA}
    \addplot[mark=none,blue] table[comment chars={@,\#}, x index=0, y index=5] {\relativepath rdf_550ns-700ns.xvg};
    \addlegendentry{CL}
    \addplot[mark=none,cyan] table[comment chars={@,\#}, x index=0, y index=6] {\relativepath rdf_550ns-700ns.xvg};
    \addlegendentry{water}
  \end{axis}
\end{tikzpicture}