Connect red to black and put the white in with the other whites. Youll have the spare yellow wire nut the pool guy put in. Fire it up just long enough to check the light. If the pool light is out of the water it will cook the gasket

The gfci will trip the instant the power is on and water hits hot wires. That's why its there. It might tingle for a half second at worst. Not much of a safety concern.