coloring single cell in smallmatrix

Question

I'm trying to color a single cell in smallmatrix, but it seems to me that the \cellcolor doesn't work in smallmatrix:

\documentclass{article}
\usepackage{amsmath} %smallmatrix
\usepackage[table]{xcolor} %cellcolor
\begin{document}
\[
\left(\begin{array}{cc}
\cellcolor{gray}1&2
\end{array}\right)
    \quad
\left(\begin{smallmatrix}
\cellcolor{gray}1&2
\end{smallmatrix}\right)
\]
\end{document}

You can see that the array is colored as desired while in smallmatrix \cellcolor doesn't do anything.

Does anyone know how to do color cells in smallmatrix?

Answer 1

You need to use the \colorbox macro. And, since the \colorbox macro typesets its second argument in text mode (and text style), be sure to encase the second argument in a $\scriptstyle ...$ "wrapper".

$(\begin{smallmatrix}
\colorbox{lightgray}{$\scriptstyle 1$}&2
\end{smallmatrix})$

A full MWE: (mininimum working example):

\documentclass{article}
\usepackage{amsmath}       % smallmatrix env.
\usepackage[table]{xcolor} % \cellcolor, \colorbox
\begin{document}

$\left(\begin{array}{cc}
\cellcolor{lightgray}1&2
\end{array}\right)$

$(\begin{smallmatrix}
\colorbox{lightgray}{$\scriptstyle 1$}&2
\end{smallmatrix})$

\end{document}