I want to fill the box but \cellcolor{red} doesn't work.
\documentclass{article}
\usepackage{float}
\usepackage{array, makecell}
\setcellgapes{5pt}
\begin{document}
\makegapedcells
\begin{tabular}{|c|c|c|c|}
\hline
\cellcolor{red}1&1&1&1\ \hline
1&1&1&1\ \hline
1&1&1&1\ \hline
1&1&1&1\ \hline
1&1&1&1\ \hline
\end{tabular}
\end{document}




\usepackage[table]{xcolor}. ■ Using https://tex.stackexchange.com/questions/185674/how-to-see-which-package-define-a-particular-command-macro you can figure out which package the commands belong to (colortbl), and figure out the issue is that makegapedcell conflicts with cellcolor in colortbl. – user202729 Dec 20 '21 at 05:34