Image fusion for 3 bands satellite image NOT correct

I try to compine 3 RGB bands for IKONOS image, but the result is not like the original image.

My image

The original

and this is my code:

     red = uint8(imread('po_58208_red_0000000.tif'));
     green = uint8( imread('po_58208_grn_0000000.tif'));
     blue = uint8(imread('po_58208_blu_0000000.tif'));
    [rows, columns, numberOfColorBands] = size(red);
    rgb = uint8(cat(3, red, blue, green));
    imshow (uint8 (rgb))

Why??