\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.text,calc,arrows.meta}
\begin{document}
\begin{tikzpicture}
\coordinate (O) at (0,0);
\draw (O) circle (2.5);
\draw (O) circle (1.5);
\draw (O) circle (0.5);
\draw[decoration={text along path,reverse path,text align={align=center},text={ss}},decorate] (0.6,0) arc (0:180:0.6);
\draw[decoration={text along path,reverse path,text align={align=center},text={Nil }},decorate] (1.6,0) arc (0:180:1.6);
\draw[decoration={text along path,reverse path,text align={align=center},text={Nilnt}},decorate] (2.6,0) arc (0:180:2.6);
\end{tikzpicture}
\end{document}
Question: Instead of writing the text on the each circle, I want to write it outside the circle with an colored array pointing to it.
See the image given below which is what I want to draw.