ok, how many metal halides and vho bulbs does that setup typically have?
What I would do, is attach a single wire to any side of a vho bulb, turn on the VHO switch, if the bulb lights up at all, then you have the right wire for it, remove it and mark it with a piece of tape, go through all the all the wires until you have the VHO bulb wires marked, now typically (atleast one would hope) that the neutral wires (ie that bring the current back) will be different colored than the hot wires. Also a typical thing is to have less neutral wires than hot wires, and have bulbs share a neutral since most of the resistance happens in the bulb so there's no worry of overheating the wire (hell the Workhorse 7 ballast has 4 hots and only 1 neutral!).
Now once you figured out which hots belong to the VHO bulbs, hook one up to a bulb, then with the VHO turned on grab one neutral (I'd guess black ones since there are less of those) and touch the other side of the VHO bulb (just touch the prongs) and you'll either see a) nothing happen, in which case that's not a neutral for the VHO, or b) the VHO bulb will get much brighter and might see a little arcing of current when you touch the prong and pull it away, which will be your VHO wire.
Your MH setup typically will have 2 wires one hot one neutral, never have heard of any sharing a neutral since they typically each have their own ballast.
Now the worst case scenario with this is the retards at Hamiliton have the same colored wiring for the VHO and same color for the MH, which is really stupid, but would make a tad of sense if the setup is for 1 MH and 2 VHO bulbs. If this is the case (ie you touch the blacks to the bulb and get no chance this might tell you that), then simply find out which ones are hot and which ones are neutral, hook up a wire to one side of the VHO bulb, then touch another wire to the other until it lights up brightly, if you put two hots(or neutrals) to a bulb it won't fire at all.
Either way find out which wire goes where using the VHO bulb(s) only, don't do this with a MH bulb.