How to remove blank spaces around table rules

Question

I am trying to produce a colored table but the separation lines and the border lines are creating blank spaces that ruins the aesthetics of the table. I wish to remove them.

Here is the code I'm using

\usepackage{multirow}
\usepackage{booktabs}
\usepackage{hhline}
\usepackage[table]{xcolor}

\begin{document}

\begin{table}[h]
\centering
\begin{tabular}{l*8cl}
\toprule
\rowcolor[HTML]{A4CAF6} 
\multicolumn{1}{c}{\cellcolor[HTML]{A4CAF6}}                            & \multicolumn{8}{c}{\cellcolor[HTML]{A4CAF6}Temperatura $[^{\circ}C]$} & \cellcolor[HTML]{A4CAF6}                             \\ \cmidrule(lr){2-9}
\rowcolor[HTML]{A4CAF6} 
\multicolumn{1}{c}{\multirow{-2}{*}{\cellcolor[HTML]{A4CAF6}Propiedad}} & 25     & 50     & 100     & 150    & 200    & 250    & 300    & 350    & \multirow{-2}{*}{\cellcolor[HTML]{A4CAF6}Referencia} \\
\rowcolor[HTML]{FFFFC7} 
$Rp_{0,2} [MPa]$                                                          &        &        &         &        &        &        &        &        &                                                      \\ 
\rowcolor[HTML]{CFCFCF} 
$UTS [MPa]$                                                               &        &        &         &        &        &        &        &        &                                                      \\ \bottomrule
\end{tabular}
\end{table}

\end{document}

Answer 1

With the lastest version of nicematrix (4.0 of 2020/05/08), you can have the result easily (you need several compilations).

\documentclass{article}
\usepackage{multirow}
\usepackage{booktabs}
\usepackage{siunitx}

\usepackage{nicematrix}

\definecolor{myblue}{HTML}{A4CAF6}
\definecolor{myyellow}{HTML}{FFFFC7}
\definecolor{mygray}{HTML}{CFCFCF}

\begin{document}

\begin{table}[h]
\centering
\begin{NiceTabular}{L*{8}{C}L}[code-before = \rowcolor{myblue}{1,2} \rowcolor{myyellow}{3} \rowcolor{mygray}{4}]
\toprule
\multirow{2}{*}{Propiedad} & \multicolumn{8}{C}{Temperatura [\si{\celsius}]} & \multirow{2}{*}{Referencia}\\
\cmidrule{2-9}
 & 25 & 50 & 100 & 150 & 200 & 250 & 300 & 350 \\
R\textsubscript{p0,2} [\si{\mega\pascal}] \\
UTS [\si{\mega\pascal}] \\
\bottomrule
\end{NiceTabular}
\end{table}

\end{document}

Answer 2

Here is my suggestion. In order to get rid of the white line, you can use \hhline{>{\arrayrulecolor[HTML]{A4CAF6}}->{\arrayrulecolor{black}}-------->{\arrayrulecolor[HTML]{A4CAF6}}->{\arrayrulecolor{black}}}. This will fill the white gap with a line in the same color as the background.

Instead of repeating the HTML color definition over and over, I suggest defining the color in the preamble and using this predefined color throughout your document. This will make thing much easier if you later on decide to change the color. You will then only have to chenge the definition in the preamble instead of changing the color of every single cell. In the following MWE I have used such a globally defined color.

I have also added the siunitx package for the units °C and MPa. I have also changed the code for Rp0,2 and UTS (assuming that these correpsond to yield strength and ultimate tensile strength) since using math mode for abbreviations is not recommended. If you want UTS to show up in italic, use \textit{UTS} instead.

For the second table, I have added the cellspace packagein order to add some vertical space above and below the text in each cell to avoid overlap with the horizontal lines.

\documentclass{article}
\usepackage{multirow}
\usepackage{booktabs}
\usepackage{hhline}
\usepackage[table]{xcolor}
\usepackage{siunitx}

\definecolor{myblue}{HTML}{A4CAF6}
\definecolor{myyellow}{HTML}{FFFFC7}
\definecolor{mygray}{HTML}{CFCFCF}

\usepackage[column=0]{cellspace}
\setlength\cellspacetoplimit{0.5\tabcolsep}
\setlength\cellspacebottomlimit{\cellspacetoplimit}
\begin{document}

\begin{table}[h]
\centering
\begin{tabular}{l*8cl}
\hline
\rowcolor[HTML]{A4CAF6} 
\multicolumn{1}{c}{\cellcolor{myblue}}                            & \multicolumn{8}{c}{\cellcolor{myblue}Temperatura [\si{\celsius}]} & \cellcolor{myblue}                             \\ 
\hhline{>{\arrayrulecolor{myblue}}->{\arrayrulecolor{black}}-------->{\arrayrulecolor{myblue}}->{\arrayrulecolor{black}}}
\rowcolor{myblue} 
\multicolumn{1}{c}{\multirow{-2}{*}{\cellcolor{myblue}Propiedad}} & 25     & 50     & 100     & 150    & 200    & 250    & 300    & 350    & \multirow{-2}{*}{\cellcolor{myblue}Referencia} \\
\rowcolor{myyellow} 
R\textsubscript{p0,2} [\si{\mega\pascal}]                                                          &        &        &         &        &        &        &        &        &                                                      \\ 
\rowcolor{mygray} 
UTS [\si{\mega\pascal}]                                                               &        &        &         &        &        &        &        &        &                                                      \\ \hline
\end{tabular}
\end{table}


\begin{table}[h]
\centering
\begin{tabular}{0l*{8}{0c}0l}
\hline
\rowcolor[HTML]{A4CAF6} 
\multicolumn{1}{c}{\cellcolor{myblue}}                            & \multicolumn{8}{c}{\cellcolor{myblue}Temperatura [\si{\celsius}]} & \cellcolor{myblue}                             \\ 
\hhline{>{\arrayrulecolor{myblue}}->{\arrayrulecolor{black}}-------->{\arrayrulecolor{myblue}}->{\arrayrulecolor{black}}}
\rowcolor{myblue} 
\multicolumn{1}{c}{\multirow{-2}{*}{\cellcolor{myblue}Propiedad}} & 25     & 50     & 100     & 150    & 200    & 250    & 300    & 350    & \multirow{-2}{*}{\cellcolor{myblue}Referencia} \\
\rowcolor{myyellow} 
R\textsubscript{p0,2} [\si{\mega\pascal}]                                                          &        &        &         &        &        &        &        &        &                                                      \\ 
\rowcolor{mygray} 
UTS [\si{\mega\pascal}]                                                               &        &        &         &        &        &        &        &        &                                                      \\ \hline
\end{tabular}
\end{table}

\end{document}