By using nicematrix package and command \Block, I'm struggling to reduce the width and height of block colors, separately. Any hint? Below, find the code:
\documentclass{article}
\usepackage{nicematrix,tikz}
\begin{document}
\begin{equation*}
\begin{bNiceArray}{cccc|c}[columns-width=5pt,margin]
\Block[fill=red]{2-4}{} a_{11} & a_{12} & a_{13} & a_{14} & \Block[fill=yellow]{3-1}{} a_{15} \\
a_{21} & a_{22} & a_{23} & a_{24} & a_{25} \\
a_{31} & a_{32} & a_{33} & a_{34} & a_{35}
\end{bNiceArray}
\end{equation*}
\end{document}

