On Wed, 16 Aug 2023, Wolfgang Schuster wrote:

> 3. \starttikzpicure doesn't allow arguments which results in font error
> messages (char ... missing). This is an error in the ConTeXt version of the
> \starttikzpicture command and should be fixed.

Looking at m-tikz.mkxl, \starttikzpicture should allow optional arguments. The following works correctly for me with ver 2023.07.18:

\usemodule[tikz]
\usetikzlibrary[patterns]
\starttext
	\starttikzpicture[scale=0.75]
	% recipient
	\draw (0,0) -- (0,10) -- (2,10) -- (2,0) -- cycle;

	% aigua
	\filldraw[pattern=north east lines, pattern color=orange] (0,0) -- (0,4) -- (2,4) -- (2,0) -- cycle;
	\draw (1,2) node[fill=white] {aigua};

	% oli
	\filldraw[pattern=dots, pattern color=blue] (0,4) -- (0,6.5) -- (2,6.5) -- (2,4) -- cycle;
	\draw (1,5.25) node[fill=white] {oli};

	% ròtuls
	\draw (2,2) node[anchor=west] {$2/5$};
	\draw (2,5.25) node[anchor=west] {$1/4$};
	\stoptikzpicture
\stoptext

Aditya