What are the possible differences between LEGO elements? I'm in a technical school in the Netherlands and we received the following questions for an assignment:


What are the other possible differences between LEGO elements?
What are the different forms of LEGO elements?
In which different colours can the LEGO elements exist?
In what packaging form can the elements be found?


Where can I find information on these various questions?
Really 4 questions in one.

To try to address question 3, 


  In which different colours can the LEGO elements exist?


these links to other similar questions may help:


How many different colours of LEGO bricks are there?
Is there a list of colours currently in production?