Change style of nodes after first alignment

Question

I have a graph which I draw with my own command. I have to use that very often but normally in different colors. There are no problems with edges becaus I simply can use \draw[style=green](x)--(y) to color the edge (x,y) green. But I also want to do that with specific nodes e.g: the node v1 should be red.

Here is my command:

\newcommand{\mygraph}{
    \node[](x) at (0,0){$x$};
    \node[](y) at (0,-4){$y$};
    \foreach \a in {1,...,5}{
        \node[](v\a) at (\a*180/6:4) {$v_\a$};
    }
    \foreach \a in {1,...,5}{
        \draw (x)--(v\a);       
    }
}

And how I use it:

\begin{figure}[h]
    \centering
    \begin{tikzpicture}
        \mygraph
        \draw[dotted](x)--(y);
        \draw[style=green](x)--(v1);
    \end{tikzpicture}
    \caption{Graph $G$}
\end{figure}

So is there a possibility to take one of the nodes and recolor it?

Answer 1

If you always have 5 nodes/path, you could define a command with optional and default arguments using the xparse parckage.

\documentclass[tikz,border=3mm]{standalone}
\usepackage{xparse}
\begin{document}
% This defines the \mygraph macro with default black colours for all node/path pair
% but you can cutsomize colours on the fly !
\NewDocumentCommand{\mygraph}{ O{black} O{black} O{black} O{black} O{black}}{
    \node[](x) at (0,0){$x$};
    \node[](y) at (0,-4){$y$};
    \foreach \a/\mycolor in {1/#1,2/#2,3/#3,4/#4,5/#5}{
        \node[\mycolor](v\a) at (\a*180/6:4) {$v_\a$};
        \draw[\mycolor] (x)--(v\a);       
    }
}
\begin{tikzpicture}
    \mygraph
\end{tikzpicture}
\begin{tikzpicture}
    \mygraph[red][][blue]
\end{tikzpicture}
\end{document}

Answer 2

You can store the colors in an array, which get used in the loop.

\documentclass[tikz,border=3mm]{standalone}
\begin{document}
\newcommand{\mygraph}{
    \node[](x) at (0,0){$x$};
    \node[](y) at (0,-4){$y$};
    \foreach \a in {1,...,5}{
        \pgfmathsetmacro{\mycolor}{{\lstColors}[\a-1]}
        \node[\mycolor](v\a) at (\a*180/6:4) {$v_\a$};
    }
    \foreach \a in {1,...,5}{
        \pgfmathsetmacro{\mycolor}{{\lstColors}[\a-1]}
        \draw[\mycolor] (x)--(v\a);       
    }
}
\edef\lstColors{"red","green","blue","orange","magenta"}
\begin{tikzpicture}
 \mygraph
\end{tikzpicture}
\end{document}