Relative column widths combined with other formatting in tables

Question

I can see that relative column widths can be achieved via the tabularx package, as laid out in this question. I want my table to span the entire text width and to provide relative column widths to indicate how space should be allocated. However, I have specific formatting already applied to my table and I cannot reconcile the implementation of my formatting and the relative column widths.

Shown below is an image of a table already produced by my minimum working example, the code for which is also below. What I have now is a table which spans the full text width. It has a header row with specific text formatting and cell coloring. The subsequent rows have alternating colored backgrounds. As it is now, the column widths are simply set to be long enough to fit the data in the table. What I'd like is to combine the features of the tabularx package (or any other package/feature which accomplishes this goal) to say that the relative widths of the columns (for the example below) should be 0.15, 0.15, 0.55, and 0.15 respectively, while still retaining the rest of the table formatting. This way, the columns actually span the full text width. I cannot find a way to do this!

---

Current Table Output

Current Minimum Working Example to Produce Table Above

\documentclass{article}

\usepackage[letterpaper,margin=1in]{geometry} % Handles geometry of page layout
\usepackage[table]{xcolor} % Colors tables nicely
\usepackage{tabularx}

\definecolor{greyblue}{rgb}{0.6353,0.6863,0.7686}
% Defines command \rowstyle for specifying style for entire row
\newcolumntype{+}{>{\global\let\currentrowstyle\relax}}
\newcolumntype{^}{>{\currentrowstyle}}
\newcommand {\rowstyle}[1]{\gdef\currentrowstyle{#1} %
    #1\ignorespaces
}

\begin{document}

{\rowcolors{2}{black!5}{black!15} % Specify alternating row colors
    \begin{table}[h]
        \label{table_1} \centering
        \begin{tabularx}{\linewidth}{ +c^c^l^c }
            \hline
            \rowcolor{greyblue} \rowstyle{\bfseries} % Specify the header row is grey-blue in color and bold
            Header 1 & Header 2 & Really Long Header 3   & Header 4 \\ % Header row
            A    & B  & CDEFGHIJKLMNOPQRSTUVWXY  & Z    \\
            1    & 2  & 345  & 6    \\
            \hline
        \end{tabularx}
    \end{table}
}

\end{document}

Answer 1

Like this?

MWE:

\documentclass{article}
\usepackage[letterpaper,margin=1in]{geometry} % Handles geometry of page layout
\usepackage[table]{xcolor} % Colors tables nicely
\usepackage{tabularx}

\definecolor{greyblue}{rgb}{0.6353,0.6863,0.7686}
% Defines command \rowstyle for specifying style for entire row
\newcolumntype{+}{>{\global\let\currentrowstyle\relax}}
\newcolumntype{^}{>{\currentrowstyle}}
\newcolumntype{C}{>{\centering\arraybackslash}X}    % <-- new
\newcolumntype{L}{>{\raggedright\arraybackslash}X}
\newcommand {\rowstyle}[1]{\gdef\currentrowstyle{#1} %
    #1\ignorespaces
}

\begin{document}

    \begin{table}[htb]
\renewcommand\arraystretch{1.2}
\rowcolors{2}{black!5}{black!15} % Specify alternating row colors
\centering
\caption{}% label has sence only if it is present
    \label{table_1}
\begin{tabularx}{\linewidth}{+>{\hsize=0.15\hsize}C ^   % <-- changed
                              >{\hsize=0.15\hsize}C ^   % <-- changed
                              >{\hsize=0.55\hsize}L     % <-- changed
                              >{\hsize=0.15\hsize}C }   % <-- changed
    \hline
\rowcolor{greyblue}\rowstyle{\bfseries} % Specify the header row is grey-blue in color and bold
Header 1    & Header 2  & Really Long Header 3      & Header 4  \\ % Header row
A           & B         & CDEFGHIJKLMNOPQRSTUVWXY   & Z         \\
1           & 2         & 345                       & 6         \\
    \hline
\end{tabularx}
    \end{table}
\end{document}