MATLAB: Using imshow and mesh in the same figure (as subplots), colour and greyscale issue

colorcolourgreyscaleimshowmesh

Hi,
I have written a piece of code to plot a greyscale image using imshow and a mesh plot using mesh in the same plot (the graphs are subplots in the smae figure. My problem is that when I use imshow the meshplot turns to greyscale rather than colour, and I can't worj out how to have one plot as greyscale and the other as colour.
My code is below if this helps;
%Script to show diffraction grating
clear all
M=dlmread('testslit5.txt','\t');
subplot(2,1,1),imshow(M);
title('Diffraction grating');
Mtransform=fft2(M);
Mtransform=fftshift(Mtransform);
N=max(max(Mtransform));
Mtransform=Mtransform/N;
subplot(2,2,3),mesh(abs(Mtransform));
title('Diffraction grating diffraction pattern (intensity)');
subplot(2,2,4),mesh(angle(Mtransform));
title('Diffraction grating diffraction pattern (phase)');
Thanks in advance
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