documentclass{article}
usepackage{tikz,pgfplots}

begin{document}
pgfplotsset{width=15cm,height=10cm}
begin{tikzpicture}
begin{axis}[colorbar sampled,colorbar style={samples=13}, grid=both, scale only axis=true,
  width=10cm, height=15cm,xtick={0,1,...,10},ytick={0,1,...,10},xmin=0,ymin=0,ymax=10,xmax=10]
addplot[
scatter,mark=text, text mark={rule{14mm}{5mm}},only marks,
point meta=thisrow{myvalue}
]
table {
x y color myvalue
2 3 1 100
4 3 2 3
2 7 3 0.75
7 7 4 45
8 5 2   3
};
end{axis}
end{tikzpicture}

end{document}


%colorbar  horizontal
%colormap/bluered,colorbar
%%colorbar  horizontal
%colorbar/width=2cm,
%colorbar sampled,colorbar style={samples=8}]
%colorbar sampled line]