[Tex/LaTex] How to get rid of left and right margins with standalone images

Question

When using the standalone package to move my images outside of the main document an annoying side effect shows up.
The standalone tex file will always have a left margin of about 0.75cm.
I can manually remove this using \useasboundingbox(0.8,0) (4.1,4.6); in the tikz code or by setting the lmargin explicitly using \usepackage[margin=1in, lmargin=1.75cm, rmargin=1.75cm]{geometry}.

The first option (\useasboundingbox) is tedious because I have to manually figure out the correct adjustments for every picture.
The second option (\usepackage{geometry}) adds a border to the right margin where there was none before, again requiring manual readjustment per image.

Here's the document in question:

% Tikz File 'mytikz.tex'
\documentclass{standalone}
\usepackage{standalone}
%\usepackage[margin=1in, lmargin=1.75cm, rmargin=1.75cm]{geometry}
\standaloneconfig{mode=image|tex}
\usepackage{tikz}
%\usetikzlibrary{...}
\usetikzlibrary{decorations.pathreplacing}
\usetikzlibrary{arrows.meta,calc}
\begin{document}
  \definecolor{light-gray}{gray}{0.98}
  \definecolor{darkgreen}{RGB}{0,64,0}
  \definecolor{lightgray}{gray}{0.75}
  \definecolor{lightred}{RGB}{255,200,200} 
  \definecolor{lightblue}{RGB}{200,200,255}
  \definecolor{lightgreen}{RGB}{200,255,200}
  \definecolor{pink}{RGB}{255,128,128}
    \begin{tikzpicture} 
    %\useasboundingbox(0.8,0) (4.1,4.6);
    \def\opacity{0.75}
    \def\xcellsa{{"A","B","C","D"}}

    \def\xcellsb{{"4","3","2","1"}}

    %bc slice
    \filldraw[lightblue, opacity=0.5] (1,0) rectangle (3,4);
    \draw[step=1,black, opacity=\opacity, fill opacity=0] (1,0) grid (3,4);
    %23slice
    \filldraw[lightblue, opacity=0.5] (0,1) rectangle (4,3);
    \draw[step=1,black, opacity=\opacity, fill opacity=0] (0,1) grid (4,3);
    %core
    \draw[fill = white, thick, dashed] (2,2) circle (0.5cm);
    \node[fill = white, opacity=1] at (2,2) {core};
    %coordinate
    \draw[fill = black] (1.5,2.6) circle (0.1cm);
    \node at (1.5, 2.6) (A) {};
    \node at (0.8,4.4) (B) {};
    \draw[-Stealth, semithick] (B) to [bend right] (A);
    \node[fill=white, opacity=1] at (1,4.4) {anchor};

    \foreach \xa in {1,2} {
      \node[align=center] at ({\xa+0.5},{4-0.5}) {\pgfmathparse{\xcellsa[\xa]}\pgfmathresult};
    }
    \foreach \ya in {1,2} {  
      \node[align=center] at ({0.5},{\ya+0.5}) {\pgfmathparse{\xcellsb[\ya]}\pgfmathresult};
    }  
  \end{tikzpicture}
\end{document}

How do I get it to render automatically with no (or very small) margins?

Answer 1

As suggested by Ulrike Fischer I moved the color definitions to the preamble.

That fixed the issue. The image now has no borders:

% Tikz File 'mytikz.tex'
\documentclass{standalone}
\usepackage{standalone}
%\usepackage[margin=1in, lmargin=1.75cm, rmargin=1.75cm]{geometry}
\standaloneconfig{mode=image|tex}
\usepackage{tikz}
%\usetikzlibrary{...}
\usetikzlibrary{decorations.pathreplacing}
\usetikzlibrary{arrows.meta,calc}
\definecolor{light-gray}{gray}{0.98}
\definecolor{darkgreen}{RGB}{0,64,0}
\definecolor{lightgray}{gray}{0.75}
\definecolor{lightred}{RGB}{255,200,200} 
\definecolor{lightblue}{RGB}{200,200,255}
\definecolor{lightgreen}{RGB}{200,255,200}
\definecolor{pink}{RGB}{255,128,128}
\begin{document}
    \begin{tikzpicture} 
    %\useasboundingbox(0.8,0) (4.1,4.6);
    \def\opacity{0.75}
    \def\xcellsa{{"A","B","C","D"}}
    
    \def\xcellsb{{"4","3","2","1"}}
    
    %bc slice
    \filldraw[lightblue, opacity=0.5] (1,0) rectangle (3,4);
    \draw[step=1,black, opacity=\opacity, fill opacity=0] (1,0) grid (3,4);
    %23slice
    \filldraw[lightblue, opacity=0.5] (0,1) rectangle (4,3);
    \draw[step=1,black, opacity=\opacity, fill opacity=0] (0,1) grid (4,3);
    %core
    \draw[fill = white, thick, dashed] (2,2) circle (0.5cm);
    \node[fill = white, opacity=1] at (2,2) {core};
    %coordinate
    \draw[fill = black] (1.5,2.6) circle (0.1cm);
    \node at (1.5, 2.6) (A) {};
    \node at (0.8,4.4) (B) {};
    \draw[-Stealth, semithick] (B) to [bend right] (A);
    \node[fill=white, opacity=1] at (1,4.4) {anchor};
   
    \foreach \xa in {1,2} {
      \node[align=center] at ({\xa+0.5},{4-0.5}) {\pgfmathparse{\xcellsa[\xa]}\pgfmathresult};
    }
    \foreach \ya in {1,2} {  
      \node[align=center] at ({0.5},{\ya+0.5}) {\pgfmathparse{\xcellsb[\ya]}\pgfmathresult};
    }  
  \end{tikzpicture}
\end{document}

Before: After: