Numbered and coloured grid using Tikz

Question

I'm trying to create a large grid with 1,000 entries, similar to what is in this link:

TikZ (finite) grid with character in each cell

I want each entry to be filled with consecutive numbers and set the background colour independently in each one. IS there a quick way to generate this list without inputing each entry manually?

Answer 1

Something like this? (with credits to zeroth and samcarter)

\documentclass[tikz, border=2mm]{standalone} 

\begin{document}
\begin{tikzpicture}[scale=1]
  \foreach \y [count=\ny from 0] in {0.5,1.5,...,49.5} {
      \foreach \x [count=\nx, evaluate=\x as \num using int(\nx+10*\ny)] in {0.5,1.5,...,19.5} {
            \pgfmathsetmacro{\R}{random(0,10000)/10000}%
            \pgfmathsetmacro{\G}{random(0,10000)/10000}%
            \pgfmathsetmacro{\B}{random(0,10000)/10000}%
            \definecolor{MyColor}{rgb}{\R,\G,\B}%
          \node[fill=MyColor,inner sep=0.1cm,outer sep=0pt,anchor=center, minimum size=1cm] at (\x,-\y) {\num}; 
      }
  }
\end{tikzpicture}
\end{document}

Complete result:

A detail:

Answer 2

For comparison here's a slightly different approach done in Metapost using the luamplib wrapper library. Compile with lualatex.

\RequirePackage{luatex85}
\documentclass[border=5mm]{standalone}
\usepackage{luamplib}
\begin{document}
\mplibtextextlabel{enable}
\begin{mplibcode}
beginfig(1);
    numeric rows, cols, u, v;
    % how big is the grid?
    rows = 13;
    cols = 8;
    % horizontal and vertical units
    u = 13mm;
    v =  8mm;
    % a nice unit box scaled slightly smaller so we get a margin
    path box;
    box = unitsquare 
          shifted -(1/2,1/2) % shifted so it's centred on (0,0)
          xscaled (u-1mm)
          yscaled (v-1mm);
    % define all the colors      
    color shade[];
    % give them all a default color,
    for i=1 upto (rows*cols): 
        shade[i] = .9[blue, white]; 
    endfor 
    % explicitly define colors for what ever cells
    shade[1]  := 1/2[red,white];
    shade[21] := 2/3[blue,white];
    shade[94] := 2/3[red+1/2green,white];
    % etc....

    numeric n;
    for c = 1 upto cols:
        for r = 1 upto rows:
            n := c + (r-1)*cols;
            fill box shifted (c*u,r*v) withcolor shade[n];
            draw box shifted (c*u,r*v);
            label(decimal n, (c*u,r*v));
        endfor
    endfor
endfig;
\end{mplibcode}
\end{document}