Histogram of color image

I made program to hide message inside image using LSB steganography. every things going ok but why I get the histogram of cover image equal the histogram of stego image? can anyone help please my code is:

subplot(4, 4, 1);
imshow(c);title(' Cover Image (Bablylon)', 'FontSize', fontSize);

subplot(4, 4, 2); 
    Red = c(:,:,1);
    Green = c(:,:,2);
    Blue = c(:,:,3);

    %Get histValues for each channel
    [yRed, x] = imhist(Red);
    [yGreen, x] = imhist(Green);
    [yBlue, x] = imhist(Blue);%Plot them together in one plot
    plot(x, yRed, 'Red', x, yGreen, 'Green', x, yBlue, 'Blue');
    title('Histogram of Cover image ', 'FontSize', fontSize);             
    subplot(4, 4, 3);
imshow(s);title(' Stego Image(Bablylon)', 'FontSize', fontSize);

subplot(4, 4, 4); 
    Red = s(:,:,1);
    Green = s(:,:,2);
    Blue = s(:,:,3);

    %Get histValues for each channel
    [yRed1, x1] = imhist(Red);
    [yGreen1, x1] = imhist(Green);
    [yBlue1, x1] = imhist(Blue);

    %Plot them together in one plot
    plot(x1, yRed1, 'Red', x1, yGreen1, 'Green', x1, yBlue1, 'Blue');
      title('Histogram of Stego image ', 'FontSize', fontSize);