How can I reset the colored image after I converted into grayscale?

I have 4.jpg as image.1st i am converting it into grayscale to apply imhist(). I am getting grayscale enhanced image as output but I need the enhanced colored image as output. How to do that? I tried using colormap as shown in code below. But its not working

I = imread('4.jpg');
imshow(I)
R = rgb2gray(I);
figure
imshow(R)
in = histeq(R);
figure;
imshow(in);
figure;
imhist(in);

y=colormap(hot(110));
   imwrite(R,y,'4.jpg','jpg'); 
   imshow('4.jpg');
%    I=imread('4.jpg');
%    R=rgb2gray(I); % It is gray now
% %    y=colormap(hot(110));
% %    imwrite(R,y,'rgb.jpg','jpg'); % Re-change it to colored one 
% %    T=imread('rgb.jpg');
% 
% imshow(T);
%  imshow('4.jpg');

Answer 1

[Guillaume]

Nothing is stopping you from performing histogram equalisation on each colour channel, if that's what you're after:

rgbimage = imread('4.jpg');
equalisedimage = rgbimage;   %copy for simplicity
for channel = 1:3   %iterate over the 3 colour channel
   equalisedimage(:, :, channel) = histeq(rgbimage(:, :, channel));  %apply histogram equalisation to each channel
end
imshowpair(rgbimage, equalisedimage, 'montage');

I would advise you to use meaningful variable names as I've done here instead of your meaningless (and misleading!) one letter variable names.

[Roshni gupta]

Thankyou so much :) its working.

[Image Analyst]

By the way, histogram equalization tends to give crummy looking images and is rarely if ever needed. For example you don't need to do it prior to doing things like thresholding, etc. I've never needed to use it in 40 years of image processing.