Dear Fabrice,

I run your code using ConTeXt LMTX and got the figure.
(LuaMetaTeX 2.00, ConTeXt version: 2019.11.14.)
I don’t know why you have errors.

Here is the beginning of log file:

resolvers       | formats | executing runner 'run luametatex format': /Users/graph/ConTeXtLMTX/tex/texmf-osx-64/bin/luametatex --jobname="test" --fmt=/Users/graph/ConTeXtLMTX/tex/texmf-cache/luatex-cache/context/5fe67e0bfe781ce0dde776fb1556f32e/formats/luametatex/cont-en.fmt --lua=/Users/graph/ConTeXtLMTX/tex/texmf-cache/luatex-cache/context/5fe67e0bfe781ce0dde776fb1556f32e/formats/luametatex/cont-en.lui cont-yes.mkiv --c:autopdf --c:currentrun=1 --c:fulljobname="/Users/graph/Documents/TeXfiles/test.tex" --c:input="/Users/graph/Documents/TeXfiles/test.tex" --c:kindofrun=1 --c:maxnofruns=9 --c:purge --c:texmfbinpath="/Users/graph/ConTeXtLMTX/tex/texmf-osx-64/bin"
This is LuaMetaTeX, Version 2.00.0 
open source     > level 1, order 1, name 'cont-yes.mkiv'
system          > 
system          > ConTeXt  ver: 2019.11.14 17:47 MKIV beta  fmt: 2019.11.19  int: english/english
system          > 
system          > 'cont-new.mkiv’ loaded


Best regards,

Dalyoung


> 
> \starttext
> \startMPcode
>   defaultfont := "texgyrepagella-regular*default" ;
>   defaultscale :=0.8;
> 
>   color brown;
>   brown = (0.128,0.00,0.00);
> 
>   path twos, threes, sixes;
>   twos = fullcircle xscaled 4cm yscaled 2cm rotated 180
>          shifted 42 left;
>   threes = fullcircle xscaled 4cm yscaled 2cm shifted 42 right;
>   sixes = buildcycle(twos, threes);
> 
>   fill twos   withcolor brown withtransparency(1,0.75);
>   fill threes withcolor yellow withtransparency(1,0.75);
>   fill sixes withcolor yellow + brown withtransparency(1,0.75);
> 
>   draw twos;
>   draw threes;
> 
>   label("...",(1.5cm,0));
>   label("...",(0,0));
>   label("...",(-1.5cm,0));
>   label.top("yeux marron",(-1.5cm,1.25cm));
>   label.top("cheveux blonds",(1.5cm,1.25cm));
> \stopMPcode
> \stoptext