Some data on voltage drop through the factory headlight harness.

First, a note on wiring. Honda put the pink wire as the common ground, with the black wire as the low beam feed and the green wire as the high beam feed in the H4 headlight plug.

Onto voltage drop, measured with my Harbor Freight digital multimeter:

Car off:
Battery: 12.5 volts
Headlight: 11.8 volts

Car on:
Battery: 14.5 volts
Headlight: 14.3 volts

I would have thought the voltage drop to be far more, given the spaghetti size of the wire. Interesting results, to say the least.