How can all labels of a given type of node be restyled in Tikz?
Imagine that there are nodes of different styles, and that only the nodes of style X should have red labels. Is this possible without having to change all labels one by one of nodes of style X?
To change it for all nodes:
\tikzset{every node/.style={<style_specs>}} If you have a custom style, you can set this only for that specific node style:
\tikzset{My Style/.style={red, draw=blue, fill=yellow!20, minimum size=0.5cm}} If you want to change an existing node style, you can use .append style to add to the nodes style specs:
\tikzset{rectangle/.append style={draw=brown, ultra thick, fill=red!30}} 
\documentclass{article} \usepackage{tikz} \tikzset{My Style/.style={red, draw=blue, fill=yellow!20, minimum size=0.5cm}} \tikzset{rectangle/.append style={draw=brown, ultra thick, fill=red!30}} \begin{document} \begin{tikzpicture} \node [My Style] at (0,0) {$x$}; \node [My Style] at (1,0) {$y$}; \node [rectangle] at (2,0) {$z$}; \end{tikzpicture} \end{document} This actual intent here is more complex that what I thought since a label is actually a node. One solution would be to define a style for each particluar shape. So, for instance, for a rectangle you could define My Rectangle as:
\tikzset{My Rectangle/.style={ rectangle, draw=brown, fill=yellow, thick, prefix after command= {\pgfextra{\tikzset{every label/.style={blue}}}} } } which alters the label style (Again, thanks to percusse):
You could also just change the rectangle style as follows:
\tikzset{rectangle/.append style={ prefix after command= {\pgfextra{\tikzset{every label/.style={blue}}}} } } \documentclass{article} \usepackage{tikz} \tikzset{My Rectangle/.style={ rectangle, draw=brown, fill=yellow, thick, prefix after command= {\pgfextra{\tikzset{every label/.style={blue}}}} } } \begin{document} \begin{tikzpicture} \node [rectangle, label=black text] at (1,0) {$z$}; \node [My Rectangle, label={blue text} ] at (3,0) {$z$}; \node [rectangle, label={blue text} ] at (5,0) {$z$}; \end{tikzpicture} \end{document} 
\tikzset defines a new style. If you want to have it applied ALL the time, then you can use \tikzset{every node/.style={My Rectangle}}. If that doesn't solve your question, perhaps you need to ask a new question. Prolog: After Peter Grill undeleted his answer my answer becomes kind of null.
But maybe someone else can profit from it in some way …
Surprisingly (to me anyway) the following will turn the node's text itself green.
\tikzset{X/.style={label/.style={green}}} \node[X,label=hello] {X}; The existing every label/.style definition apparently works only in a scope-like usage.
\begin{scope}[every label/.style={green}] \node[X,label=hello] {X}; % and a lot of other X nodes \end{scope} Adding the every label/.style to the definition of X fails (with no change to the output):
\tikzset{X/.style={every label/.style={green}}} \node[label=hello] {X}; The /.style can have one argument:
\tikzset{X/.style={ % your styles here, e.g. draw, circle, % and … label={[green]#1} } } \node[X=hello] {X}; \node[X={[draw]hello}] {Y}; % this fails, you can't add an extra optional argument I'd use the .style args key handler, where one can set the argument pattern to [#1]#2. Note, that the [] are not mandatory!
The key handler .style 2 args has also two arguments where the second one is optional, but it requires you to write X={hello} or X={hello}{draw}.
\documentclass{standalone} \usepackage{tikz} \begin{document} \begin{tikzpicture} \tikzset{X/.style args={[#1]#2}{ % your styles here, e.g. draw, circle, % and … label={[green,#1]#2} } } \node[X={[]hello}] {X}; \node[X={[draw]hello}] at (1,0) {Y}; \node[X={[red]hello}] at (2,0) {Z}; \end{tikzpicture} \end{document} 
I believe there is a solution hidden in the answers of Optional arguments in pgfkeys?. But they all appear to require to write [draw]{hello}.
