\documentclass{article}
\usepackage{graphicx}
% \usepackage{amsfonts}
% \usepackage{amsmath}
% \usepackage{verbatim}
\usepackage{tikz}
\usetikzlibrary{arrows}
\tikzstyle{male}=[circle,fill=blue!20,draw,font=\sffamily\Large\bfseries]
\tikzstyle{female}=[circle,fill=red!20,draw,font=\sffamily\Large\bfseries]
\begin{document}
\begin{figure}[!htb]
\begin{tikzpicture}[->,>=stealth',shorten >=1pt,auto,node distance=3cm,thick, main node/.style={circle,draw,fill=red!20,font=\sffamily\Large\bfseries}]
\node[main node] (1) {1};
\node[main node] (2) [below left of=1] {2};
\node[main node] (3) [below right of=2] {3};
\node[main node] (4) [below right of=1] {4};
\path[every node/.style={font=\sffamily\small}]
(1) edge node {} (3)
edge [bend right] node[left] {} (2)
(2) edge node {} (4)
edge node {} (1)
(3) edge node[left] {} (2)
edge [bend right] node[right] {} (4)
(4) edge node[left] {} (3);
\end{tikzpicture} %
\end{figure}
\end{document}
答案1
要仅为指向给定节点（在本例中）的边添加颜色3，请将选项添加到任何链接的[color-name]键中。例如：edgei -> 3
...(4) edge[red] node[left] {} (3);