Why SAVEAS function saves the created image with different colors?

I try to plot multiple images, which are intensity color maps and then save them as separate files. The saved image is then different from the one in the pop-up window. it seems like the color scale is changed from jet to parula. Any ideas how to resolve this? Manual saving doesn't work for 1000 images and 'PaperPositionMode' didn't do its job as described in MathLab Answers.

for i = 1:time
    colormap jet;
    figure  
    imagesc(x_nm(:), y_nm(:), E_x(:,:,i));
    set(gcf, 'PaperPositionMode', 'auto')
    colorbar;
    set(gca,'FontSize',18);
    set(gca,'xtick',[])
    set(gca,'ytick',[])
    fname = sprintf('int_map_at_%d', i);
    saveas(gcf,fname,'png')
end