Those are connected to your tail lights of your tow vehicle. The red lights on the rear of the vehicle which are illuminated while the headlight switch is in the on position.
In the case of a motor boat trailer, Green wyre is starboard turn and brake signal. Yaller wyre is port turn and brake signal. Brown wyre is "running" lights, the lights that are on constantly when the headlight switch is on. Two small red on each rear corner and two red rear sides of the trailer behind trailer axle, also two amber sides ahead of trailer axle
White wire is ground, to make the trailer frame connection to the vehicle frame. Always connect this wire, don't rely on the trailer ball to make the connection. First of all, your trailer lights will flicker as you bounce down the road, which is irritating and the lights may not work when they're really important, or they may not work properly. 2nd reason is flickering lights will burn out a regular incandescent bulb quickly.
Also remember to disconnect your trailer lights from the vehicle while backing the trailer into the water b/c unless your lights are completely sealed from water (waterproof), a hot glass incandescent bulb(not modern LED type) will crack the glass when it hits the relatively cold water, ruining the bulb.