\usemodule[tikz]

% This worked in 2012.05.14
\definecolor[light orange]
  [h=30,s=0.33,v=1]

% But works with next line uncommented:
%\colorlet{light orange}{orange!33}

\starttext

\starttikzpicture
\draw[light orange] (0,0) -- (10,10);
\stoptikzpicture

\stoptext
