The headlights were lifted and held up by pneumatic struts. There was a cable latch on them, and when you pulled the cable the struts lifted the lights. You had to push the lights back down by hand.
BTW, I think it was only the bumper that was painted half-and-half. That was done so that the team cars were easier to differentiate.
For tons and tons of 914-6GT information, see:
http://www.pbase.com/9146gt
For info on the strut/cable headlight kits, see:
http://www.pbase.com/9146gt/gt_mechanical_headlight_raisers
--DD