How to fill the space between two \draw lines

using double :

\documentclass{standalone}
\usepackage{pgfplots}
\usetikzlibrary{patterns}

\begin{document}
\begin{tikzpicture}
  \draw[double=green] (3.1,4.2) -- (2.45,3.8);
\end{tikzpicture}
\begin{tikzpicture}
  \draw[double=green, double distance=.1cm] (3.1,4.2) -- (2.45,3.8);
\end{tikzpicture}
\begin{tikzpicture}
  \draw[double=green, double distance=.2cm] (3.1,4.2) -- (2.45,3.8);
\end{tikzpicture}
\end{document}