如何用一半一半的颜色绘制边框

Question

在下面的代码中，我如何在圆圈周围画线，使得一半是蓝色，一半是红色（双色圆圈边框）？

\node[circle, draw=blue,line width=.5mm] at (0, 0) [label=center:{($A$)}] (A) {};

Answer 1

这就是我们dash patterns的用途。以下是一些基本示例。

\documentclass[tikz,border=3mm]{standalone}
\begin{document}
\begin{tikzpicture}
\node[circle, draw=blue,dash pattern=on pi*0.5em off pi*0.5em,
postaction={draw=red,dash phase=pi*0.5em},
,line width=.5mm,minimum size=1em] at (0, 0) [label=center:{($A$)}]  (A) {};
\node[circle, draw=blue,dash pattern=on pi*1em off pi*1em,
postaction={draw=red,dash phase=pi*1em},
,line width=.5mm,minimum size=2em] at (2, 0) [label=center:{($A$)}]  (A) {};
\end{tikzpicture}
\end{document}

显然，您可以将其设为一种风格。（如果需要拼写出来，请告诉我。）

Answer 2

\documentclass[tikz,margin=3mm]{standalone}

\begin{document}
    \begin{tikzpicture}[line width=.5mm]
\draw[red] (-0.5,0) arc (180:0:0.5);
\draw[blue] (0.5,0) arc (360:180:0.5);
\node {$(A)$};
    \end{tikzpicture}
\end{document}