Booktabs Cell Coloring Overflow and Position Bias

Question

I want to fill booktabs table cells in a custom manner. I did two examples as below, one with kerning and the other is straight booktabs table. The first problem is in both tables, coloring that is not at the table border overflows up to the border of the next column (the red line in the image indicates this). The second problem is kerning macros (or whatever they are called), distracts the positioning of cell texts, as seen in the image. The texts are biased to bottom of the cell.

• How can I prevent overflowing in single cell coloring?
• How can I remove position bias? (Maybe this can be inherently fixed after finding a solution to the first question)

\begin{table}[b!]
    \centering
    \caption{Kern'ed Table.}
    \label{tab:graphExplanation}
    %\renewcommand{\arraystretch}{1.15}
    \extrarowheight=\aboverulesep
    \addtolength{\extrarowheight}{\belowrulesep}
    \aboverulesep=0pt
    \belowrulesep=0pt
    \begin{tabular}{>{\kern-\tabcolsep}cccc<{\kern-\tabcolsep}} 
        \toprule
        
        \multicolumn{2}{c}{MulC1} 
        & \multicolumn{2}{c}{MulC2}  \\
        \cmidrule(r){1-2} 
        \cmidrule(r){3-4}
        
        \textbf{Col1} & \textbf{Col2} & \textbf{Col1} & \textbf{Col2}  \\
        
        Cell & \cellcolor[HTML]{C0C0C0} Cell & Cell & \cellcolor[HTML]{C0C0C0}Cell \\
        
        Cell &  \cellcolor[HTML]{C0C0C0}Cell & Cell &  \cellcolor[HTML]{C0C0C0}Cell \\
        \bottomrule
    \end{tabular}
\end{table}
\begin{table}[b!]
    \centering
    \caption{UnKern'ed Table.}
    \label{tab:graphExplanation}
    %\renewcommand{\arraystretch}{1.15}

    \begin{tabular}{@{}cccc@{}} 
        \toprule
        
        \multicolumn{2}{c}{MulC1} 
        & \multicolumn{2}{c}{MulC2}  \\
        \cmidrule(r){1-2} 
        \cmidrule(r){3-4}
        
        \textbf{Col1} & \textbf{Col2} & \textbf{Col1} & \textbf{Col2}  \\
        
        Cell & \cellcolor[HTML]{C0C0C0} Cell & Cell & \cellcolor[HTML]{C0C0C0}Cell \\
        
        Cell &  \cellcolor[HTML]{C0C0C0}Cell & Cell &  \cellcolor[HTML]{C0C0C0}Cell \\
        \bottomrule
    \end{tabular}
\end{table}

Answer 1

Here are two examples using an empty column between the first two and the last two columns:

Instead of lines from the booktabs package, I used regular \hline and \cline commands. In order to symmetrically increase the row heights of the table, I either used the cellspace package or the corresponsing options from the nicematrix package.

You can of course change the spacing above and below the text, as well as left and right of the text in a cell to your liking. Adding \setlength{\tabcolsep}{3pt} will for example result in the following output:

\documentclass{article}

%%%%%%%%%% used in the first example %%%%%%%%%%%%%%%%%
\usepackage[column=0]{cellspace}
\setlength{\cellspacetoplimit}{4pt}
\setlength{\cellspacebottomlimit}{\cellspacetoplimit}
\usepackage{colortbl}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%



%%%%%%%%%% used in the second example %%%%%%%%%%%%%%%%
\usepackage{nicematrix}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{document}



    \begin{tabular}{0c0c0l0c0c} 
        \hline
        \multicolumn{2}{0c}{MulC1} 
        && \multicolumn{02}{c}{MulC2}  \\
        \cline{1-2} \cline{4-5}
        
        \textbf{Col1} & \textbf{Col2} && \textbf{Col1} & \textbf{Col2}  \\
        
        Cell & \cellcolor[HTML]{C0C0C0}Cell && Cell & \cellcolor[HTML]{C0C0C0}Cell \\
        
        Cell &  \cellcolor[HTML]{C0C0C0}Cell && Cell &  \cellcolor[HTML]{C0C0C0}Cell \\
        \hline
    \end{tabular}
    
\bigskip

\NiceMatrixOptions{cell-space-top-limit = 5pt,cell-space-bottom-limit = 5pt}
\begin{NiceTabular}{cclcc}[code-before =\cellcolor{lightgray}{3-2,3-5,4-2,4-5}]
\hline
        \multicolumn{2}{c}{MulC1} 
        && \multicolumn{2}{c}{MulC2}  \\
        \cline{1-2} \cline{4-5}
        
        \textbf{Col1} & \textbf{Col2} && \textbf{Col1} & \textbf{Col2}  \\
        
        Cell & Cell && Cell & Cell \\
        
        Cell &  Cell && Cell &  Cell \\
        \hline
\end{NiceTabular}

\end{document}

Answer 2

With the excellent nicematrix package there is no problem

\documentclass{article}
\usepackage{nicematrix}
\usepackage{booktabs}

\begin{document}
\begin{NiceTabular}{lccc}
\CodeBefore
  \cellcolor{blue!30}{3-2,4-2,3-4,4-4}
\Body
  \toprule[2pt]
  \Block{1-2}{MulC1} && \Block{1-2}{MulC2} \\
  \cmidrule(l){1-2} \cmidrule(l){3-4}
  \RowStyle{\bfseries}
  Col1 & Col2 & Col1 & Col2 \\
  Cell & Cell & Cell & Cell \\
  Cell & Cell & Cell & Cell \\
  \bottomrule[2pt]
\end{NiceTabular}
\end{document}

Answer 3

Just guessing (to long for comment). Do you like to have the following table:

For it is using part of each table. Also are changed \cmidrules:

\documentclass{article}          
\usepackage{booktabs}
\usepackage[table]{xcolor}


\begin{document}
    \begin{table}[b!]
    \centering
    \caption{Kern'ed Table.}
    \label{tab:graphExplanation}
\begin{tabular}{>{\kern-\tabcolsep}cccc }
    \toprule
\multicolumn{2}{c}{MulC1}                   & \multicolumn{2}{c}{MulC2}         \\
    \cmidrule{1-2}
    \cmidrule(l){3-4}

\textbf{Col1}   & \textbf{Col2}             & \textbf{Col1} 
                                                    & \textbf{Col2}             \\
Cell            & \cellcolor{gray!50}{Cell} & Cell  & \cellcolor{gray!50}{Cell} \\
Cell            & \cellcolor{gray!50}{Cell} & Cell  & \cellcolor{gray!50}{Cell} \\
    \specialrule{\heavyrulewidth}{0pt}{2pt}
\end{tabular}
    \end{table}
\end{document}

Edit:

• content of last column is centered
• bottomrule is replaced by \specialrule

Addendum: IN the case, that you like to add \midrule between column headers and table body, you can do this with \specialrule{\lightrulewidth}{2pt}{0pt}:

\begin{tabular}{>{\kern-\tabcolsep}cccc }
    \toprule
\multicolumn{2}{c}{MulC1}                   & \multicolumn{2}{c}{MulC2}         \\
    \cmidrule{1-2}
    \cmidrule(l){3-4}

\textbf{Col1}   & \textbf{Col2}             & \textbf{Col1}
                                                    & \textbf{Col2}             \\
    \specialrule{\lightrulewidth}{2pt}{0pt}
Cell            & \cellcolor{gray!50}{Cell} & Cell  & \cellcolor{gray!50}{Cell} \\
Cell            & \cellcolor{gray!50}{Cell} & Cell  & \cellcolor{gray!50}{Cell} \\
    \specialrule{\heavyrulewidth}{0pt}{2pt}
\end{tabular}

which gives: