TikZ - multi-color double circle node

Question

How do I draw a node with a double circle shape where one circle has a different color than the other circle?

A single \node[whatever] {content} would be nice!

Answer 1

Here's a new style double circle that can be supplied to a node. It takes two arguments, one for specifying how much larger the radius of the outer circle is (default is 2pt), and the second for specifying the colour (or any combination of options, really) of the inner circle (default is blue).

If you specify a node name, this will refer to the outer node (thanks to Andrew Stacey for the suggestion).

\node (A) [double circle, draw=red] {b};
\node (B) at (2,0) [draw, double circle={-2pt}{orange}] {ABC};
\draw (A) -- (B);

will give you

\documentclass[border=4mm] {standalone}

\usepackage{tikz}
\usetikzlibrary{calc}

\begin{document}
\tikzset{
    old inner xsep/.estore in=\oldinnerxsep,
    old inner ysep/.estore in=\oldinnerysep,
    double circle/.style 2 args={
        circle,
        old inner xsep=\pgfkeysvalueof{/pgf/inner xsep},
        old inner ysep=\pgfkeysvalueof{/pgf/inner ysep},
        /pgf/inner xsep=\oldinnerxsep+#1,
        /pgf/inner ysep=\oldinnerysep+#1,
        alias=sourcenode,
        append after command={
        let     \p1 = (sourcenode.center),
                \p2 = (sourcenode.east),
                \n1 = {\x2-\x1-#1-0.5*\pgflinewidth}
        in
            node [inner sep=0pt, draw, circle, minimum width=2*\n1,at=(\p1),#2] {}
        }
    },
    double circle/.default={2pt}{blue}
}


\begin{tikzpicture}
\node (A) [double circle, draw=red] {b};
\node (B) at (2,0) [draw, double circle={-2pt}{orange}] {ABC};
\draw (A) -- (B);
\end{tikzpicture}%
%
\end{document}

Answer 2

Not sure exactly what you want, but here are five different ways:

\documentclass[border=2pt]{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
% Version 1
\draw [red ] (0,0) circle (5pt);
\draw [blue] (0,0) circle (10pt);
\node at     (0,0) {1};

% Version 2
\node [draw=blue,double=red, circle, inner sep=1pt] at (1,0) {2};

% Version 3
\draw [draw=red, inner sep=1pt]  (2,0) circle (8pt);
\node [draw=blue, circle, inner sep=1pt] at (2,0) {3};

% Version 4
\path (3,0) node [draw=red,shape=circle]  {}
      (3,0) node [draw=blue,shape=circle] {4};

% Version 5 (similar to Version 2)
\path (4,0) node [draw=blue, shape=circle, double=red] {5};
\end{tikzpicture}
\end{document}

Answer 3

great job, I used your code to start a vertical timeline..

\usetikzlibrary[calc,arrows,decorations.pathmorphing,backgrounds,positioning,fit,petri,shapes,mindmap,shadows]

\tikzset{
    old inner xsep/.estore in=\oldinnerxsep,
    old inner ysep/.estore in=\oldinnerysep,
    double circle/.style 2 args={
        circle,
        old inner xsep=\pgfkeysvalueof{/pgf/inner xsep},
        old inner ysep=\pgfkeysvalueof{/pgf/inner ysep},
        /pgf/inner xsep=\oldinnerxsep+#1,
        /pgf/inner ysep=\oldinnerysep+#1,
        alias=sourcenode,
        append after command={
        let     \p1 = (sourcenode.center),
                \p2 = (sourcenode.east),
                \n1 = {\x2-\x1-#1-0.8*\pgflinewidth}
        in
            node [inner sep=0.01pt, draw,circle, fill, minimum width=1*\n1,at=(\p1),#2] {}
        }
    },
    double circle/.default={2.5pt}{blue!50}
}
\begin{tikzpicture}[
nonterminal/.style={rectangle,minimum size=6mm,very thick,draw=red!50!black!50,top color=white, bottom color=red!50!black!20,font=\itshape},
%{ The shape:, The size:, The border:, 50 % red and 50% black, and that mixed with 50% white,  The filling:, a shading that is white at the top...,and something else at the bottom, Font}
terminal/.style={rectangle,minimum size=6mm,rounded corners=3mm,very thick,draw=black!50,top color=white,bottom color=black!20,font=\ttfamily},
line width=4pt,
circulo/.style={circle,minimum size=3mm,line cap=rect,draw=blue!50,top color=white,bottom color=blue!40,font=\ttfamily}
]
\node (A) [double circle, draw=blue!20] {};
\node (B) [double circle, draw=blue!20][below=of A] {};
\node (C) [double circle, draw=blue!20][below=of B] {};
\node (D) [double circle, draw=blue!20][below=of C] {};
\node (E) [double circle, draw=blue!20][below=of D] {};
\node (F) [double circle, draw=blue!20][below=of E] {};
\node (G) [double circle, draw=blue!20][below=of F] {};
\node (H) [double circle, draw=blue!20][below=of G] {};
\draw[-] [blue!20] (A) -- (H);
\node (B1) [rectangle, minimum size = 6mm][below=of A,label=right:Primeira Etapa, label=left:2008] {};

\end{tikzpicture}