It seems unlikely that the lines could leak coolant as there is none in them. The lines carry a refrigerant to/from an evaporator. Moisture on the cold parts of the system is normal and a drain allows it to drip out at the rear. Even in the desert, you'll often see moisture there.

Remember that there is both refrigerant and oil in the system. If leaking, as TeeSter says the refrigerant dissipates quickly. But the oil remains. If there's a puddle, it could be oil. The refrigerant oil is a very bright yellow-green, almost fluorescent. It would be easy to think it's coolant, as both have oily textures and your coolant is also a yellow-green color.

Although I'm sorry to hear of your problem, I admit this is interesting and that I'm curious to to hear what your tech finds.

If it's leaking badly, cooling should be diminishing. Does the A/C work?

Don't discount the humidity theory, BTW. I live in a semi-arid climate, and often the weather people will say the humidity here is low, like 15-20%. But even on those days, A/C systems on our cars drip water.