Water level sender connection help.

Had a water leak from the exit point on my water tank, pipe running to tap and having searched this forum discovered that the tank to pipe connection is screw connection that if it becomes loose you can not tighten from the exterior, it appears that a previous owner had same issue and fixed with silicone. Here is my problem, someone in the past has cut the twin cable from the level sender unit and repaired with terminal block connection, all cables were dirty so I attached a cable tie to two of the cables that were connected as a marker, so that i could identify which two were connected, my marker fell off so. 
Two grey cables from sender unit, one solid black, one black white stripe from interior, any advice pls on what should connect to each other, thanks.

It may be worth waiting to see if anyone else with exactly the same van comes along to advise, but as a generic observation, on a vehicle with a plastic tank it should not matter which way round you connect the wires.

There are a couple of types of system - one based on a float with a resistance, and the other on pairs of probes, but as long as it's just a pair of wires it should work either way round.

Thank you.

I was overthinking this, connect two wires, did not work, changed around , worked.
So tank leak repaired, tested today, tank cleaned, 4 new “J” bolts on way, angle iron supports cleaned and repainted, wooden plywood under tray cleaned, stained with preservative, van ext floor undersealed. 
Earlier this week I fitted new Bilstein Shock absorbers and replaced the foam dashboard  vent seals, Been a busy few days.