Blue top HGH has a yellow flip off top (not to be mistaken with white or orange)
Blue top HGH s a blue flip off top
Seriously they are made by different labs thus different colour code, you can also get Red or Green HGH.
Blue is considered the cheapest as its been around for ages (no necessary made by the same lab) theres lots of reviews about them good and bad, people are willing to pay $30 extra hoping that different colour top will make all the difference and the product will be better.
BTW I get mine goodies straight from the lab, colour code differs almost every time I order.