title: why indexing ndarray of picture like this makes picture green and blue?
body: <pre><code>   import numpy as np
      from skimage import io 
      import matplotlib.pyplot as plt
      
      jeju = io.imread('jeju.jpg')
  
      jeju.shape 
  
  &gt; (960,1280,3)
  
      jeju
  
  &gt; Array([[[171, 222, 251],
          [172, 223, 252],
          [172, 223, 252],
          ...,
          [124, 189, 255],
          [121, 189, 254],
          [120, 188, 253]],
  
         [[173, 224, 253],
          [173, 224, 253],
          [173, 224, 253],
          ...,
          [124, 189, 255],
          [122, 190, 255],
          [121, 189, 254]],
  
         [[174, 225, 254],
          [174, 225, 254],
          [175, 226, 255]
          ...,
          [125, 190, 255],
          [122, 190, 255],
          [122, 190, 255]],
  
         ...,
  
         [[ 66,  93,  26],
          [ 89, 114,  46],
          [ 49,  72,   2],
          ...,
          [  2,  29,   0],
          [ 34,  59,  17],
          [ 40,  63,  21]],
  
         [[ 44,  71,   4],
          [ 23,  50,   0],
          [ 29,  52,   0],
          ...,
          [ 40,  67,  22],
          [  0,  19,   0],
          [ 16,  41,   0]],
  
         [[ 29,  58,   0],
          [ 44,  71,   2],
          [ 84, 110,  37],
          ...,
          [ 17,  44,   1],
          [ 33,  60,  17],
          [ 18,  43,   1]]], dtype=uint8)
      
      plt.imshow(jeju)
  
  
      
      plt.imshow(jeju[:,:,0])
  
  
  
      jeju[:,:,0]
  
  &gt;Array([[171, 172, 172, ..., 124, 121, 120],
         [173, 173, 173, ..., 124, 122, 121],
         [174, 174, 175, ..., 125, 122, 122],
         ...,
         [ 66,  89,  49, ...,   2,  34,  40],
         [ 44,  23,  29, ...,  40,   0,  16],
         [ 29,  44,  84, ...,  17,  33,  18]], dtype=uint8)
  
      ---------------------------------------------
  
      
  </code></pre>
  <p>As above, I read picture from directory and index it to make picture red.
  Because (960, 1280, 3) from <code>jeju.shape</code> is (height,width,rgb) and I thought that if I used <code>[:,:,0]</code>, 0 meant red.( I thought r=0,g=1,b=2)
  But result was not red picture but picture full of green and blue.
  Why this thing happened? What <code>[:,:,0]</code> means in real?</p>
  <p><img src="https://i.stack.imgur.com/laCjf.png" alt="" />
  <img src="https://i.stack.imgur.com/ixt7a.png" alt="" /></p>