I wanted to have table with light gray color for its borders.

So I wrote this

-----------------------
\documentclass[12pt]{book}%
\usepackage{longtable}

\usepackage{xcolor,colortbl}
\definecolor{lightgray}{rgb}{0.83, 0.83, 0.83}
\arrayrulecolor{lightgray}

\begin{document}

\begin{longtable}{|p{2in}|p{2in}|p{2in}|}\hline
A&B&C \\ \hline
A&B&C \\ \hline
A&B&C \\ \hline
\end{longtable}
\end{document}
-------------------------

It works OK in pdf.

But Compiled with

make4ht -ulm default -a warning A.tex 'mathjax,htm'

Gives HTML with the table missing all the horizontal table edges between the rows.

Removing the commands

\usepackage{xcolor,colortbl}
\definecolor{lightgray}{rgb}{0.83, 0.83, 0.83}
\arrayrulecolor{lightgray}

Now all the table borders show up. (using default black color).

TL 2024