I have the 5.5v (Moki), 5.9v & 7.4v versions of the Sparkswitch in my box of parts. I need help in identifying which one is which. The 5.5v has a stamp on it, so I can easily identify, but the others do not. Does blue label = 5.9v, black = 7.4v? I have a blue, but is doesn't have an output voltage.