Subject: What is the reasoning why the onion skin is not green?

I was in my bio class, performing a lab that dealt with the examining of cells 
(frog cells, human blood cells and onion skin cells.) When I was examining the 
onion skin cells, we put an drop of iodine stain on the onion skin and observed 
it at about 430X. We stain the skin to make it easier to see.  Without the 
stain the skin is clear. I know that plant cells are typically green. What is 
the logical reasoning why the onion skin is NOT green? What type of plant 
structure is an onion, and what is its specific function?

Re: What is the reasoning why the onion skin is not green?