Decorate path with just a colored thick line

Question

Is it possible to decorate a path with just a thick colored line above or below it? In the following example I faked manually the result, but how can I do it with decorations? In particular I want to be able to choose the color and the line width and use the raise option of the decoration.

\documentclass{article}

\usepackage{tikz}
\usetikzlibrary{calc}
\begin{document}

\begin{tikzpicture}
   \coordinate (A) at (0,0);
   \coordinate (B) at (1,1);
   \coordinate (v) at ($(B) - (A)$);

   \path let \p1 = (v) in ($1/(\x1^2 + \y1^2)^(0.5)*(\y1,-\x1)$) coordinate (p);
   \pgfmathsetmacro{\dist}{0.7}
   \coordinate (AA) at ($(A) + \dist*(p)$);
   \coordinate (BB) at ($(B) + \dist*(p)$);

   \draw (A) -- (B);
   \draw[thick,orange] (AA) -- (BB);
\end{tikzpicture}
\end{document}

Edit: If it is not possible to get it via decorations is it possible to define a style just for straight lines which allows you to draw two or three colored lines just like here: http://tex.stackexchange.com/a/36858/4011 in the case of circles.

Answer 1

Will using double help here?

\documentclass{standalone}
\usepackage[svgnames]{xcolor}
\usepackage{tikz}
\usetikzlibrary{calc}
\begin{document}

\begin{tikzpicture}
   \coordinate (A) at (0,0);
   \coordinate (B) at (1,1);
   \coordinate (v) at ($(B) - (A)$);

   \path let \p1 = (v) in ($1/(\x1^2 + \y1^2)^(0.5)*(\y1,-\x1)$) coordinate (p);
   \pgfmathsetmacro{\dist}{0.7}
   \coordinate (AA) at ($(A) + \dist*(p)$);
   \coordinate (BB) at ($(B) + \dist*(p)$); 
   \draw[line width=5pt,orange,double=black,double distance=1pt] (AA) -- (BB);

   \begin{scope}[xshift=4cm]
   \draw[very thick, orange,double=black,double distance=1pt] (-0.1,5) .. controls (-4,-2) and (4,-2) .. (0.1,5);
   \end{scope}

\end{tikzpicture}
\end{document}