You could shade it if you make the paths closed.
This is based on Mark Wibrow's code, as quoted in the question.
% answer to https://tex.stackexchange.com/questions/314918/generate-coloured-fancy-delaunay-patterns-in-tikz, modifying code by Mark Wibrow at https://tex.stackexchange.com/a/260652/
\documentclass[tikz,border=10pt,multi,rgb]{standalone}
% xcolor manual: 34
\definecolorseries{colours}{hsb}{grad}[hsb]{.575,1,1}{.987,-.234,0}
\resetcolorseries[12]{colours}
\tikzset{%
set my colour/.code={%
\colorlet{mycolour}{colours!!+},
},
my colour/.style={%
set my colour,
bottom color=mycolour,
top color=mycolour!50,
fill opacity=.5,
},
}
\begin{document}
\begin{tikzpicture}
\foreach \i [evaluate={\ii=int(\i-1)}, remember=\i as \ilast] in {0,...,7}{
\foreach \j [evaluate={\jj=int(\j-1)}, remember=\j as \jlast] in {0,...,7}{
\coordinate [shift={(\j,\i)}] (n-\i-\j) at (rand*180:1/4+rnd/8);
\ifnum\i>0
\path [my colour] (n-\i-\j) -- (n-\ii-\j) -- (n-\ilast-\j) -- cycle;
\fi
\ifnum\j>0
\path [my colour] (n-\i-\j) -- (n-\i-\jj) -- (n-\i-\jlast) -- cycle;
\path [my colour] (n-\i-\jlast) -- (n-\i-\jj) -- (n-\i-\j) -- cycle;
\ifnum\i>0
\path [my colour] (n-\i-\j) -- (n-\i-\jj) -- (n-\ii-\j) -- cycle;
\path [my colour] (n-\ilast-\j) -- (n-\ilast-\jj) -- (n-\i-\j) -- cycle;
\pgfmathparse{int(rnd>.5)}
\ifnum\pgfmathresult=0
\path [my colour] (n-\ilast-\jlast) -- (n-\ilast-\jj) -- (n-\ii-\jj) -- cycle;
\path [my colour] (n-\ilast-\j) -- (n-\ilast-\jj) -- (n-\ii-\jj) -- cycle;
\path [my colour] (n-\i-\jlast) -- (n-\i-\jj) -- (n-\ii-\jj) -- cycle;
\path [my colour] (n-\i-\j) -- (n-\i-\jj) -- (n-\ii-\jj) -- cycle;
\path [my colour] (n-\ii-\j) -- (n-\i-\jj) -- (n-\i-\j) -- cycle;
\else
\path [my colour] (n-\ii-\j) -- (n-\i-\jj) -- (n-\i-\j) -- cycle;
\path [my colour] (n-\i-\j) -- (n-\i-\jj) -- (n-\ii-\jj) -- cycle;
\path [my colour] (n-\i-\jlast) -- (n-\i-\jj) -- (n-\ii-\jj) -- cycle;
\path [my colour] (n-\ilast-\j) -- (n-\ilast-\jj) -- (n-\ii-\jj) -- cycle;
\path [my colour] (n-\ilast-\jlast) -- (n-\ilast-\jj) -- (n-\ii-\jj) -- cycle;
\fi
\fi
\fi
}
}
\end{tikzpicture}
\end{document}
