\documentclass{standalone}
\usepackage{luamplib}
\begin{document}
\begin{mplibcode}
vardef equilateral_triangle_point(expr a, b) =
 b shifted -a rotated 60 shifted a
enddef;
beginfig(1);
 path c; c = fullcircle scaled 144;
 numeric n; n = 11;
 for i=0 upto n-1:
   pair a,b,p,q;
   a = point 8/n * i of c;
   b = point 8/n * (i + 1) of c;
   p = equilateral_triangle_point(a,b);
   q = equilateral_triangle_point(b,a);
   draw a -- p -- b withcolor .67 green;
   draw a -- q -- b withcolor .67 red;
 endfor
 draw c withcolor .53 blue;
endfig;
\end{mplibcode}
\end{document}