Try this:
[rows, columns, slices] = size(m);
m8 = uint8(255 * mat2gray(m)); % Convert to 0-255;
blackImage = zeros(rows, columns, 'uint8'); % Create an invisible image for the blue channel.
% Create an RGB image with slice 1 in red, slice 2 in green, and blue as invisible.
rgbImage = cat(3, m8(:, :, 1), m8(:, :, 2), blackImage);
imshow(rgbImage, 'InitialMagnification', 1000);
axis('on', 'image')
impixelinfo; % Let user mouse around and see values.
Also see attached demo.
