[Tex/LaTex] Setting node label’s size and color in TiKZ

Question

I'm drawing AVL trees using the first answer given at AVL Trees in TikZ: draw outside of node as an example.

All I want to do is add a style definition which will draw the labels in a small font and in blue. I can of course do that individually for each label, but it would be more elegant to set it as a style. The style I have so far is

\begin{tikzpicture}[
  level/.style={sibling distance=60mm/#1},
  every node/.style={draw,circle},
  label distance=-1mm]

which works fine – but how do I add blue text and small font size to those labels?

Note that I create each label by its angle and text:

node [label=30:\small $1$] {6}

or for a color

node [label={[blue]30:\small $1$}] {6}

Anyway, I'd like to format the labels as part of the style. Thanks!

Answer 1

There is no problem whatsoever to make the label font blue and small in the answer you are referring to.

\documentclass{standalone}
\usepackage{tikz}
\begin{document}

\begin{tikzpicture}[level/.style={sibling distance=60mm/#1},
  every node/.style={draw,circle},
  label distance=-1mm,
   edge from parent path=
    {(\tikzparentnode.south) .. controls +(0,-.5) and +(0,.5)
                             .. (\tikzchildnode.north)},
   every node/.style={draw,circle},
   label distance=-1mm]
\node [label={[font=\small,text=blue]30:$-1$}]{50}
  child {node[label={[font=\small,text=blue]30:$-1$}] {10}}
  child {node[label={[font=\small,text=blue]30:$0$}] {20}
  child {node[label={[font=\small,text=blue]30:$-1$}] {10}}
  child {node[label={[font=\small,text=blue]30:$-1$}] {20}}
};
\end{tikzpicture}
\end{document}

It is easy enough to turn this into a style.

\documentclass{standalone}
\usepackage{tikz}
\begin{document}

\begin{tikzpicture}[level/.style={sibling distance=60mm/#1},
  every node/.style={draw,circle},
  label distance=-1mm,
   edge from parent path=
    {(\tikzparentnode.south) .. controls +(0,-.5) and +(0,.5)
                             .. (\tikzchildnode.north)},
   every node/.style={draw,circle},
   label distance=-1mm,
   my label/.style n args={2}{label={[font=\small,text=blue]#1:#2}}]
\node [my label={30}{$-1$}]{50}
  child {node[my label={30}{$-1$}] {10}}
  child {node[my label={30}{$0$}] {20}
  child {node[my label={-30}{$-1$}] {10}}
  child {node[my label={-60}{$-1$}] {20}}
};
\end{tikzpicture}
\end{document}