As you know, in Burrows-Wheeler Transform the matrix of all the rotations is but conceptual, and what matters is the last column. I wanted to convey this idea in the picture
\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{matrix,positioning}
\begin{document}
\begin{tikzpicture}
\begin{scope}
\matrix (B) [matrix of nodes, ampersand replacement = \&]{
{} \& {} \& {} \& {} \& {} \& {} \& {} \& {} \& {} \& {} \& {BWT} \& {SA} \\
\hline
{a} \& {n} \& {k} \& {u} \& {k} \& {l} \& {u} \& {k} \& {s} \& {k} \& {l} \& {9} \\
{k} \& {l} \& {a} \& {n} \& {k} \& {u} \& {k} \& {l} \& {u} \& {k} \& {s} \& {7} \\
{k} \& {l} \& {u} \& {k} \& {s} \& {k} \& {l} \& {a} \& {n} \& {k} \& {u} \& {2} \\
{k} \& {s} \& {k} \& {l} \& {a} \& {n} \& {k} \& {u} \& {k} \& {l} \& {u} \& {5} \\
{k} \& {u} \& {k} \& {l} \& {u} \& {k} \& {s} \& {k} \& {l} \& {a} \& {n} \& {0} \\
{l} \& {a} \& {n} \& {k} \& {u} \& {k} \& {l} \& {u} \& {k} \& {s} \& {k} \& {8} \\
{l} \& {u} \& {k} \& {s} \& {k} \& {l} \& {a} \& {n} \& {k} \& {u} \& {k} \& {3} \\
{n} \& {k} \& {u} \& {k} \& {l} \& {u} \& {k} \& {s} \& {k} \& {l} \& {a} \& {10} \\
{s} \& {k} \& {l} \& {a} \& {n} \& {k} \& {u} \& {k} \& {l} \& {u} \& {k} \& {6} \\
{u} \& {k} \& {l} \& {u} \& {k} \& {s} \& {k} \& {l} \& {a} \& {n} \& {k} \& {1} \\
{u} \& {k} \& {s} \& {k} \& {l} \& {a} \& {n} \& {k} \& {u} \& {k} \& {l} \& {4} \\
};
\filldraw[semitransparent] (B-1-1.north west) rectangle (B-12-10.south east);
\end{scope}
\end{tikzpicture}
\end{document}
The effect I would like to achieve is to somehow "blur" the contents of the matrix except for the last column. Do I have to play around with postactions in the matrix options? I could have, of course, explicitly set the relevant elements of the matrix with paler colours, so that the overall blurred effect would be achieved, but is there any way to blur entire regions?