The black wire is called ground but what is the red wire called?
Wire colors are arbitrary. Probably the red wire is a power supply wire, but it could be anything.
The most common term I've heard for this is source.
In single phase AC circuits it's hot (ungrounded). In three phase AC circuits it's A phase. In DC circuits it's positive.
There are standards for wire colours but they vary between countries and industries. When I grew up in the UK black was used for negative power and red for positive power (e.g. ground and +12V). But trailer wiring in Canada seems to use black for +12V, for instance. In a digital electronic circuit, using silicon semiconductors, ground or 0V is often abbreviated GND and the +ve power supply as Vcc.
