如何仅修改longtable表头行的边框颜色？

可以实现该需求，核心是通过\arrayrulecolor命令临时切换表格边框颜色，仅作用于表头行，之后再恢复默认颜色即可。

修改关键点 #

在定义printDbBreakableTable环境时，针对表头部分做如下调整：

1. 在表头行背景色设置前，用\arrayrulecolor{<目标颜色>}设置边框颜色（示例中用白色配合黑色表头背景，对比度更高）
2. 表头行内容结束后，用\arrayrulecolor{black}恢复默认边框颜色，避免影响表格其他行

修改后的完整代码 #

\documentclass[11pt]{book}
\usepackage[default]{opensans}
\usepackage{alltt}
\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{array}
\usepackage{colortbl}
\usepackage{enumitem}
\usepackage{fancyhdr}
\usepackage{float}
\usepackage[total={15.24cm,22.86cm}]{geometry}
\usepackage{graphicx}
\usepackage{hyperref}
\usepackage{inconsolata}
\usepackage{listings}
\usepackage{longtable}
\usepackage{mathabx}
\usepackage{microtype}
%
% For creating new commands with an arbitrary number of arguments
\usepackage{newfile}
%
%
\usepackage{pgfplots}
\usepackage{pifont}
\usepackage{smartdiagram}
\usepackage{tabularx}
\usepackage[listings,skins,most]{tcolorbox}
\usepackage{tikz}
\usepackage[table,xcdraw]{xcolor}
%
%
%
%
% Define a header style command
\newcommand{\longTabHeaderstyle}[1]{\textcolor{white}{#1}}
%
%
%
%
% Space before the table
\setlength{\LTpre}{0pt}
%
% Space after the table
\setlength{\LTpost}{0pt}
%
% Space from the left before the table
\setlength{\LTleft}{0pt}
%
% Space from the right after the table
\setlength{\LTright}{0pt}
%
%
% Define the printDbBreakableTable environment
\newenvironment{printDbBreakableTable}[4]{%
  \getLTwidth
  % Start the tcolorbox
  \begin{tcolorbox}[%
    % Make the box content breakable across pages
    breakable,%
    text width={\LTwidth},
    %
    % Set background color of the box
    colback=white,%
    %
    % Set frame color of the box
    colframe=black,%
    %
    % Set space below the title
    bottomtitle=1mm,%
    %
    % Set space above the title
    toptitle=1mm,%
    %
    % Set thickness of left border
    leftrule=0.15mm,%
    %
    % Set thickness of right border
    rightrule=0.15mm,%
    %
    % Set thickness of bottom border
    bottomrule=0.15mm,%
    %
    % Center the title
    title=\centering #1,%
    %
    % Remove internal padding
    boxsep=0pt,%
    %
    % Remove top padding
    top=0pt,%
    %
    % Remove bottom padding
    bottom=0pt,%
    %
    % Remove left padding
    left=0pt,%
    %
    % Remove right padding
    right=0pt%
  ]%
  \par
  %
  % Begin table structure by indicating the number of columns
  \begin{longtable}%
    {#2}%
    %
    % 临时设置表头边框颜色为白色
    \arrayrulecolor{white}%
    % Set header row color
    \rowcolor{black}%
    %
    % The content of the header row
    #3%
    % 恢复边框颜色为默认黑色
    \arrayrulecolor{black}%
    \endhead
    \hline
    %
    % Insert the table's main content
    #4%
  \end{longtable}%
  % End the tcolorbox
  \end{tcolorbox}%
}

\makeatletter
\newlength{\LTwidth}
\newcommand{\getLTwidth}[1][empty]% #1 = longtable index (optional)
{\bgroup% for count1 and LT@entry
  \ifx\empty#1\relax
    \count1=\value{LT@tables}% default
    \advance\count1 by 1
  \else
    \count1=#1\relax
  \fi
  \@ifundefined{LT@\romannumeral\count1}{\LTwidth=\textwidth}{%
    \LTwidth=0pt%
    \def\LT@entry##1##2{\advance\LTwidth by ##2}%
    \csname LT@\romannumeral\count1\endcsname
  }%
  \global\LTwidth=\LTwidth
\egroup}
\makeatother


\begin{document}


\addtolength{\extrarowheight}{2pt}
\begin{printDbBreakableTable}
  {Test a long table}
  {c|c|c|c}
  {%
    \longTabHeaderstyle{H1} & \longTabHeaderstyle{H2} &
    \longTabHeaderstyle{H3} & \longTabHeaderstyle{H4} \\\hline }
  {%
CellValue-1-1 & CellValue-2-1 & CellValue-3-1 & CellValue-4-1 \\\hline
CellValue-1-2 & CellValue-2-2 & CellValue-3-2 & CellValue-4-2 \\\hline
CellValue-1-3 & CellValue-2-3 & CellValue-3-3 & CellValue-4-3 \\\hline
CellValue-1-4 & CellValue-2-4 & CellValue-3-4 & CellValue-4-4 \\\hline
CellValue-1-5 & CellValue-2-5 & CellValue-3-5 & CellValue-4-5 \\
  }
  
\end{printDbBreakableTable}

\end{document}

效果说明 #

修改后，表头行的横向分隔线、纵向列分隔线都会变为设置的白色，与黑色的表头背景形成强烈对比，大幅提升表头辨识度，而表格主体行的边框仍保持默认黑色，互不影响。

内容的提问来源于stack exchange，提问作者user17911