Consider creating an indexed image instead of a bar chart. Then you can write each bar as a column with the gray level of the color you want. Apply the colormap and that column of pixels will show up in the desired color.
If you want a color gradient in each bar, then that is more complicated - you'd have to write a ramp of pixel levels rather than a constant pixel level that corresponds to the tallest color.
rows = 100;
columns = 100;
indexedImage = zeros(rows, columns, 'uint8');
for col = 1 : 100
row1 = rows-col+1
indexedImage(row1:rows, col) = col;
end
imshow(indexedImage);
colormap(gca, jet(rows));
caxis([0, rows]);
colorbar;
Modify as needed.
