....Hmmm, i can't remember witch is the colour, but you can find it.
Take a polymeter, turn it to mVDC or 2VDC, splice CAREFULLY (with gentle) cables of λ. Start your engine. After 1 minute, take one terminal of polymeter to (-) of battery and check with the other terminal, cables of λ.
At idle you must read a fluctuate rate beetween 200mv and 800mv aka 0,2v-0,8V.
This is your cable... connect your signal AFR there...
At other cables you may read 0,00V or battery charge (13.5v).
looks a lot but it is not...