Concatenate array (Bayer pattern)

I have a problem regarding concatenating three arrays R,G and B. These arrays consist of a color channel R=red, G=green and B=blue from a raw image with Bayer-pattern RGGB. A 2x2 cell looks like the following

R = 
  0.0014         0
       0         0
G =
  0         0.0049
  0.0044         0
B =
  0              0
  0         0.0022

When I'm concatenate them with cat(3,R,G,B) the cell looks like this:

0.0031           0
0                0

But when I'm trying to fill a new matrix with the values like this:

0.0014      0.0049
0.0044      0.0022

I get an grey image instead of a RGB-colored one. What am I missing?

[Pratham Shah]

How did you get this 2nd cell of [0.0031,0;0,0]? Can you explain that, because cat(3,R,G,B) will just stack these 3 metrices.