i want to shuffle the pixels of an color image using keys which is generated by chaotic map.But i get black and white image instead of color image.

clc;
clear all;
close all;
%split to rgb planes
img = imread('lenacolor32.tif'); % Read image
red = img(:,:,1); % Red channel
% figure, imshow(red), title('red')
green = img(:,:,2); % Green channel
% figure, imshow(green), title('green')
blue = img(:,:,3); % Blue channel
% figure, imshow(blue),title('blue')
a = zeros(size(img, 1), size(img, 2));
% figure, imshow(a),title('a')
R = cat(3, red, a, a);
G = cat(3, a, green, a);
B = cat(3, a, a, blue);
figure, imshow(img), title('Original image');
figure, imshow(R), title('Red plane');
figure, imshow(G), title('Green plane');
figure, imshow(B), title('Blue plane');
[r,c,n]=size(img);   
id=fix(r/3);
im1=img(1:id,:,:);
im2=img(id+1:2*id,:,:);
im3=img(2*id+1:r,:,:);
op1=horzcat(im1,im2,im3);
figure, imshow(op1),title('Horizontal format');
maxpointsp = 25; 
Np = 3074;
ap = 0;
bp = 4; 
rsp = linspace(ap,bp,Np); 
Mp = 500;
for j = 1:length(rsp)

      rp=rsp(j);
      xp=zeros(Mp,1); 
      xp(1) = 0.5;   
      a1p=4-rp;
       for i=1:Mp
          if (xp(i)<=0.5 )
              xp(i+1)=mod(((rp*xp(i))/2+(a1p*sin(pi*xp(i)))/4),0.999); 
          else
               xp(i+1)=mod(((rp*(1-xp(i)))/2+(a1p*sin(pi*(1-xp(i)))/4)),0.999);         
          end
   end
      outp{j} =xp(end-maxpointsp:end);
  end
   datap = [];
  for k = 1:length(rsp)
       n = length(outp{k});
      datap = [datap; rsp(k)*ones(n,1),outp{k}];
   end
  %  hp=plot(datap(:,1),datap(:,2),'k.'); 
   opp=datap(:,2).*3074;
   resp=round(opp);

   ap =resp;
   [bp,m1,n1] = unique(ap);
   [c1,d1] =sort(m1);
   bp = bp(d1);
   pkey=bp;%final key

   pkey=vec2mat(pkey,96);

   %pixel perm
  actu2=zeros(size(img));
  actu2=img(:,:,:);
  chang2=zeros(size(actu2));
  chang2=actu2(:,:,:);
  for r=1:1:32
      for c=1:1:96 
       if(pkey(r,c)==0);
       else
       actu2(r,c,:)=chang2(pkey(r,c),:);  
       end
      end 
  end
  figure, imshow(actu2),title('Pixel permutation');

[Guillaume]

i get black and white image instead

Your code is very convoluted but if I read it correctly the only thing it can produce without erroring is a black image. If the else branch of your last if is executed then

actu2(r,c,:)=chang2(pkey(r,c),:);

will produce an error (unless the image is only 3 pixels wide)