Hello guys

I think the basic idea behind the Groove colors is:

port A (red) : default usage I2C port B (black) : default usage I/O port C (blue) : default usage UART port A/B/C (white) : no default usage (like on the M5StickCPlus)

But it's like @teastain already said: most ports can be used for anything as the GPIOs are mostly configurable.