1 \section{Nuances of \Index{transparency}}
3 The key value \texttt{\Lkeyword{opacity}=$k$} with $k \in \mathbb{R}$ and $0\leq
4 k\leq 1$, allows you to define the level of \Index{opacity}.
6 Within \textit{jps code}, we use an equivalent expression
7 \texttt{$k$ setfillopacity}. The last expression finds its application in the option \Lkeyword{fcol}. For example the instruction,
8 \verb+fcol=0 (.5 setfillopacity yellow)+,
9 which defines the face with the index number 0, sets it to yellow with an opacity of 50\%.