Get 3 color channels, RGB, of image, and stack it together to get color image.

color_imaging.m

clear all;
%Read the image
img = imread('image.jpg'); 

%Get the size (rows and columns) of the image 
[r,c] = size(img);
rr=r/3;
%Wrire code to split the image into three equal parts and store them in B, G, R channels

B=imcrop(img,[1,1,c,rr-1]);
G=imcrop(img,[1,1*rr+1,c,rr-1]);
R=imcrop(img,[1,2*rr+1,c,rr]);

%concatenate R,G,B channels and assign the RGB image to ColorImg variable
ColorImg(:,:,1) = R;
ColorImg(:,:,2) = G;
ColorImg(:,:,3) = B;
imshow(ColorImg)

This source code crop the channel of the image below.
The topmost is blue channel, the middle is green, and the last is red.

concatenated into a stacked colored image like this.