Enviropro 3 core cable:
6-15V V+ = Brown
SDI12 data = Blue
GND = Yellow/Green
Enviropro 4 core cable:
6-15V V+ = Red
SDI12 data = Blue
GND = Black
See Wasp2 SDI12 M12 wiring standard: https://outpost.zendesk.com/hc/en-us/articles/204618389-SDIM12-Connector