Creating a Table fitting the line width and without thin white vertical lines between color filled cells

Question

Can some help me making the table coded in this Thread https://tex.stackexchange.com/a/301036/229635 fit the line width?

As a MWE I copied the code from the Thread I attached as a link.

Thanks a lot, Cheers Benson_G

\documentclass[a4paper,12pt, enabledeprecatedfontcommands, toc = sectionentrywithdots]{scrartcl} %Art des Dokuments, Schriftgröße etc. , idxtotoc, bibtotoc,
\usepackage[onehalfspacing]{setspace} %Zeilenabstand
\usepackage[hmargin={3cm,2cm},vmargin=2cm, includehead]{geometry}%Maße für die wissenschaftliche Arbeit
\usepackage[scaled=0.9]{helvet}
\renewcommand{\familydefault}{\sfdefault}
\usepackage[T1]{fontenc}
\usepackage[latin9]{inputenc}
\usepackage{array}
\usepackage{hhline}
\usepackage{color}
\usepackage{colortbl}
 \definecolor{gr}{RGB}{240,240,240}
\usepackage{tabularx}
\usepackage{babel}

\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.15pt}
\renewcommand*\ShowFrameColor{\color{red}}


\begin{document}

\noindent
\begin{tabularx}{\textwidth}{XXXX}
    \hhline{----}
    \multicolumn{1}{>{\centering\columncolor{gr}}m{.1\textwidth}} {Here's a box\\ Score} 
            & \multicolumn{1}{>{\centering\columncolor{gr}}m{.3\textwidth}}{Here's a box\\ Score}
                        & \multicolumn{1}{>{\centering\columncolor{gr}[\dimexpr\tabcolsep + 0pt\relax]}m{.3\textwidth}}{Another Box\\ with two Rows} %
                                    & \multicolumn{1}{>{\centering\columncolor{gr}[\tabcolsep]}m{.3\textwidth}|}{Student's\\ Proficiency Level}
    \tabularnewline%
    \hline
    Science     & 28    & 26 or above     & Proficient\tabularnewline
    \hline
  \end{tabularx}

\end{document} 

Answer 1

Here is a first rough version of your table that now fits into the textwidth.

\documentclass[a4paper,12pt, toc = sectionentrywithdots]{scrartcl}
\usepackage[onehalfspacing]{setspace}
\usepackage[hmargin={3cm,2cm},vmargin=2cm, includehead]{geometry}
\usepackage[scaled=0.9]{helvet}
\renewcommand{\familydefault}{\sfdefault}
\usepackage[T1]{fontenc}
\usepackage[latin9]{inputenc}
\usepackage{array}
\usepackage{hhline}
%\usepackage{color}
%\usepackage{colortbl}
\usepackage[table]{xcolor} % replaces above two lines
 \definecolor{gr}{RGB}{240,240,240}
\usepackage{tabularx}
\usepackage{babel}

\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.15pt}
\renewcommand*\ShowFrameColor{\color{red}}

\renewcommand{\tabularxcolumn}[1]{m{#1}}
\newcolumntype{Y}{>{\centering\arraybackslash}X}

\begin{document}

\noindent
\begin{tabularx}{\textwidth}{>{\centering\arraybackslash}m{.1\textwidth}YYY}
        \hhline{----}
        \multicolumn{1}{>{\centering\columncolor{gr}}m{.1\textwidth}} {Here's a box\\ Score} 
                & \multicolumn{1}{>{\centering\columncolor{gr}}X}{Here's a box\\ Score}
                            & \multicolumn{1}{>{\centering\columncolor{gr}[\dimexpr\tabcolsep + 0pt\relax]}X}{Another Box\\ with two Rows} %
                                        & \multicolumn{1}{>{\centering\columncolor{gr}[\tabcolsep]}X|}{Student's\\ Proficiency Level}
        \tabularnewline%
        \hline
        Science     & 28    & 26 or above     & Proficient\tabularnewline
        \hline
\end{tabularx}
    
\end{document} 

---

With the help of cellspace:

\documentclass[a4paper,12pt, toc = sectionentrywithdots]{scrartcl}
\usepackage[onehalfspacing]{setspace}
\usepackage[hmargin={3cm,2cm},vmargin=2cm, includehead]{geometry}
\usepackage[scaled=0.9]{helvet}
\renewcommand{\familydefault}{\sfdefault}
\usepackage[T1]{fontenc}
\usepackage[latin9]{inputenc}
\usepackage{array}
\usepackage{hhline}
%\usepackage{color}
%\usepackage{colortbl}
\usepackage[table]{xcolor} % replaces above two lines
 \definecolor{gr}{RGB}{240,240,240}
\usepackage{tabularx}
\usepackage{babel}

\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.15pt}
\renewcommand*\ShowFrameColor{\color{red}}

\renewcommand{\tabularxcolumn}[1]{m{#1}}
\newcolumntype{Y}{>{\centering\arraybackslash}X}

\usepackage[column=0]{cellspace}
\setlength{\cellspacetoplimit}{20pt}
\setlength{\cellspacebottomlimit}{\cellspacetoplimit}
\addparagraphcolumntypes{X}
\begin{document}

\noindent
\begin{tabularx}{\textwidth}{>{\centering\arraybackslash}m{.1\textwidth}YYY}
        \hhline{----}
        \multicolumn{1}{>{\centering\columncolor{gr}}0{m{.1\textwidth}}} {Here's a box\\ Score} 
                & \multicolumn{1}{>{\centering\columncolor{gr}}0{X}}{Here's a box\\ Score}
                            & \multicolumn{1}{>{\centering\columncolor{gr}[\dimexpr\tabcolsep + 0pt\relax]}0{X}}{Another Box\\ with two Rows} %
                                        & \multicolumn{1}{>{\centering\columncolor{gr}[\tabcolsep]}0{X}|}{Student's\\ Proficiency Level}
        \tabularnewline%
        \hline
        Science     & 28    & 26 or above     & Proficient\tabularnewline
        \hline
\end{tabularx}
    
\end{document} 

Answer 2

Hey guys and @leandriis,

I could manage to solve my problems by myself.

Here is what the final code looks like....just in case you are interested: It includes a way:

1. to solve the prob with white thin vertical lines between the color filled cells by using @leandriis code in this thread above

2. to only change the row height of the first row by using

\usepackage{stackengine} % Package to change row height
\newcommand\xrowht[2][0]{\addstackgap[.5\dimexpr#2\relax]{\vphantom{#1}}} 

in the preamble and \xrowht{10pt}within the multicolumn curly brackets for text. (How to specify the row height in LaTeX table?)

3. to add vertical space only between two specific cells with \addlinespace[0.2cm] right after the command for a new tabular line (Inserting a small vertical space in a table)

\documentclass[a4paper,12pt, enabledeprecatedfontcommands, toc = sectionentrywithdots]{scrartcl} %Art des Dokuments, Schriftgröße etc. , idxtotoc, bibtotoc,
\usepackage[onehalfspacing]{setspace} %Zeilenabstand
\usepackage[hmargin={3cm,2cm},vmargin=2cm, includehead]{geometry}%Maße für die wissenschaftliche Arbeit
\usepackage[parfill]{parskip} %Bessere Seitenumbrüche
\usepackage[T1]{fontenc} %Silbentrennung
\usepackage[german]{babel} %Sprachanpassungen
\usepackage{ragged2e} %für Blocksatzschalter \justifying
% \usepackage[utf8]{inputenc} %Direkte Angabe von Umlauten möglich 
\usepackage{csquotes}
\usepackage{graphicx} %Einfügen von Bildern
% \usepackage{tabularx} %Tabellen
% \usepackage{booktabs} %Weitere Möglichkeiten für Tabellen
\usepackage{here} %Lage von Tabellen und Bildern 
\usepackage{physics}
\usepackage{amsmath}
\usepackage{mathrsfs}
\usepackage{textgreek}
\usepackage{textcomp}
\usepackage{amssymb}
% \usepackage[labelformat=simple]{subcaption}
\usepackage{float}
\usepackage{pdfpages}
\usepackage{lmodern} 
\usepackage{enumitem}
\usepackage{parskip}
\usepackage[hyphens]{url} % be sure to specify the option 'hyphens'
% \usepackage[pdftex,bookmarksnumbered,hidelinks,breaklinks]{hyperref}
% \usepackage[superscript]{cite}

% ======SCHRIFTART=================================

% Schriftart Helvetica
\usepackage[scaled]{helvet}
\renewcommand\familydefault{\sfdefault}

% ===================================================

\usepackage[per-mode = reciprocal, output-decimal-marker={,}, exponent-product = {\cdot}]{siunitx} %Si-Einheiten


\usepackage[headsepline,automark, draft = false]{scrlayer-scrpage} %Für Kopf und Fußzeile und Seitenzahlen
\clearpairofpagestyles
\ihead{\headmark}
\rohead{\pagemark}
% \cfoot{\pagemark}
\addtokomafont{pageheadfoot}{\upshape}
\KOMAoptions{onpsinit={\linespread{1}\selectfont}}

%=======TABELLEN=====================================
\usepackage{booktabs, tabularx}  

\newcolumntype{Y}{>{\centering\arraybackslash}X}

\usepackage{stackengine} % Für Zeilenabstand
\newcommand\xrowht[2][0]{\addstackgap[.5\dimexpr#2\relax]{\vphantom{#1}}}

\renewcommand\tabularxcolumn[1]{m{#1}}

\usepackage[version=4]{mhchem}  % newest version
\usepackage{siunitx}% instead of units, which is deprecate
\sisetup{detect-weight,detect-mode}%Si-Einheiten
\usepackage[labelsep = period, skip=1ex, format=plain, font=small, labelfont=bf, justification = justified]{caption}     % new
%\usepackage[labelformat=simple]{subcaption}
\usepackage{colortbl}
\definecolor{ExpBlau}{rgb}{0.11,0.19,0.46}
\definecolor{gr}{rgb}{0.90,0.90,0.90}

%=====================================================
%=====================================================

\begin{document}

\renewcommand{\tablename}{Tabelle}
\renewcommand{\figurename}{Abbildung}
\captionsetup[table]{justification = raggedright, font=normal, singlelinecheck=false}

\begin{table}[htb!]
  \centering
  \footnotesize
  \setlength\belowcaptionskip{5 pt}
  \caption{\textbf{Molekulare Eigenschaften der P(EO-\textit{co}-EPB)-Copolymere$^{\textcolor{ExpBlau}a}$}}
\noindent
\begin{tabularx}{\textwidth}{>{\centering\arraybackslash}m{.04\textwidth}>{\centering\arraybackslash}m{.185\textwidth}YYYY}
    
        \multicolumn{1}{>{\centering\columncolor{gr}}m{.04\textwidth}} {\xrowht{10pt}Nr.} 
                    & \multicolumn{1}{>{\centering\columncolor{gr}[\dimexpr\tabcolsep + 0.3pt\relax]}m{.185\textwidth}} {\xrowht{10pt}Copolymer} 
                            & \multicolumn{1}{>{\centering\columncolor{gr}[\dimexpr\tabcolsep + 0.3pt\relax]}X}{\xrowht{10pt}$\textit{M}_\text{n, NMR}$ (\si{\gram\per\mole})}
                                        & \multicolumn{1}{>{\centering\columncolor{gr}[\dimexpr\tabcolsep + 0.3pt\relax]}X}{\xrowht{10pt} mol\% EPB$^{\textcolor{ExpBlau}c}$} %
                                                    & \multicolumn{1}{>{\centering\columncolor{gr}[\dimexpr\tabcolsep + 0.3pt\relax]}X}{\xrowht{10pt}$\textit{M}_\text{n, GPC}$ (\si{\gram\per\mole})} %
                                                                & \multicolumn{1}{>{\centering\columncolor{gr}[\tabcolsep]}X}{\xrowht{10pt} \textit{Đ}}
        \tabularnewline\addlinespace[0.2cm]  
                                                                                                                                                          %  SASSK
                            1                             &    ThatsALongWord    &  xxxx  &  x,x  &  xxxx  &  x,xx \tabularnewline      %   113
                            2                             &    ThatsALongWord    &  xxxx  &  x,x  &  xxxx  &  x,xx \tabularnewline      %   114
           \hspace{ 0.5mm}  3$^{\textcolor{ExpBlau}b}$    &    ThatsALongWord    &  xxxx  &  x,x  &  xxxx  &  x,xx \tabularnewline      %   101
                            4                             &    ThatsALongWord    &  xxxx  &  x,x  &  xxxx  &  x,xx \tabularnewline      %   111
                            5                             &    ThatsALongWord    &  xxxx  &  x,x  &  xxxx  &  x,xx \tabularnewline      %   105
                            6                             &    ThatsALongWord    &  xxxx  &  x,x  &  xxxx  &  x,xx \tabularnewline      %   112
\end{tabularx}
    \vspace{0.6 \baselineskip} \\
    \justifying
    $^{\textcolor{ExpBlau}a}$ Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello
  \label{tab:Copo}
\end{table}

\end{document}