Why did LEGO create different canister for the Visorak? I have the six original Visorak (Sets 8742, 8743, 8744, 8745, 8746 and 8747) with different canisters (or boxes). 

For example, my Suukorak (8747) has a white canister, and my friend's has a black one. 

Here's a picture showing the canisters: 

Some canisters are colored the same as their lid while others are black. 

Why?
I heard a similar question about old cars and how one owner had a hood made of steel and another . . . same make, same model, same year . . . had an aluminum hood. The answer as to why was simple . . . it's the metal the manufacturer had at the time. My guess is once the molding machines are loaded with a color they keep using it until it runs out. Some of the colors were versatile and looked good on multiple sets so they could make more of those before switching colors.