I want to draw an arbitrary domain which I can split in two along an arbitrary curve so I can colour both subdomains using different colours. I tried drawing the domain using the hobby library, however I don't know how to colour it separately. I attach the code of what I tried below.
\documentclass[tikz]{standalone}
\usetikzlibrary{hobby}
\begin{document}
\begin{tikzpicture}[use Hobby shortcut,closed=true]
\fill[draw=black, fill=orange] (-3.5,0.5) .. (-3,2.5) .. (-1,3.5).. (1.5,3).. (4,2.5).. (5,0.5) ..(2.5,-2).. (0,-1.5).. (-2.5,-2).. (-3.5,0.5);
\draw[black] (-3.5, 0.5) to [out=0, in=-135] (-1.5,1) to[out=45, in=-118] (1.5,0) to[out=62, in=150] (5,0.5);
\node[above] at (0,1.5) {Colour A};
\node[above] at (0, -1) {Colour B};
\end{tikzpicture}
\end{document}
Thank you very much!