When a pill is made, they are made in batches, either by the same person or people that don't even know each other. Xtc is cut with things like speed and caffeine to get the pill to stick together, as well as using food colouring. Usually, the colour of the pill is literally just that, a mere colour. Food colouring has been added to make them more visually pleasing.

As for where they make it, fuck knows, labs i guess, or home-labs.

Each pill is different from the last, the dude making the drug doesn't check to make sure that the amount of mdma in one of his pills is identical to the amount of mdma in another one of his pills, because it would take far too long.

As for shapes, same as colours, visually pleasing, open to a wider market.