how to add tip for a curve to make it look likes an arrow

Question

I would like to draw a filled arrow around a circle. So far my picture is

I need to add tip at the end of the green curve in the above picture. I would like to be able to add tips for either sides. How can I do that.

\documentclass[]{article}
\usepackage[margin=1cm]{geometry}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{calc,fit,arrows, positioning}
\usepackage{graphicx}
\usetikzlibrary{calc}



\begin{document}


\begin{tikzpicture}[auto,node distance=3cm,>=stealth']
\coordinate (O) at (5,0);

\draw [very thick,fill=blue,fill opacity=.1] 
( 5, 0) circle (2.0cm) node [opacity=1] {B} ;

\draw[fill=green]
($(O) + (0:23mm)$) arc (0:180:23mm) -- ($(O) + (180:24mm)$) arc (180:0:24mm) -- cycle;

\end{tikzpicture}

\end{document}

Answer 1

Something like this?

\documentclass[border=10pt,tikz]{standalone}
\usetikzlibrary{calc,arrows.meta}

\begin{document}

  \begin{tikzpicture}[auto,node distance=3cm,>={Stealth[width=4mm, length=6mm, fill=green]}]
    \coordinate (O) at (5,0);

    \draw [very thick,fill=blue,fill opacity=.1]
    ( 5, 0) circle (2.0cm) node [opacity=1] {B} ;

    \draw[double=green, double distance=1mm, <->]
    ($(O) + (0:23.5mm)$) arc (0:180:23.5mm);

  \end{tikzpicture}

\end{document}

EDIT

If you have an old version of TiKZ, the above will not work. In that case, you should either update your TeX distribution (recommended) or, if you're unable to do that, try this instead:

\documentclass[border=10pt,tikz]{standalone}
\usetikzlibrary{calc,arrows}

\begin{document}

  \begin{tikzpicture}[auto,node distance=3cm,>=stealth']
    \coordinate (O) at (5,0);

    \draw [very thick,fill=blue,fill opacity=.1]
    ( 5, 0) circle (2.0cm) node [opacity=1] {B} ;

    \draw[double=green, double distance=1mm, <->, green]
    ($(O) + (0:23.5mm)$) arc (0:180:23.5mm);

  \end{tikzpicture}

\end{document}

Answer 2

Here is solution (using my answer to Arrow with two colors with TikZ):

\documentclass[margin=2mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{calc,arrows}
\tikzset{
  double arrows/.style args={#1 colored by #2 and #3}{
    >=stealth,
    <->,line width=#1,#2, % first arrow
    postaction={draw,<->,#3,line width=(#1)/3,
                shorten <=2*(#1)/3,shorten >=2*(#1)/3}, % second arrow
  }
}

\begin{document}
\begin{tikzpicture}
\coordinate (O) at (5,0);

\draw [very thick,fill=blue,fill opacity=.1] 
(O) circle (2.0cm) node [opacity=1] {B} ;

\draw[double arrows=1.5mm colored by black and green]
($(O) + (0:23mm)$) ++(0,-1.5mm) -- ++(0,1.5mm) arc (0:180:23mm) -- ++(0,-1.5mm);
\end{tikzpicture}%
\end{document}