You did not mention if you have a fuse panel in the hardtop.
I looked at the diagram on your page 7-17 and its a crappy drawing. Does not identify wires to the light.
I looked at my manual and it only shows a Blue feed from fuse panel, Blue/white to spreaders, and ground(black)... which is not what is actually in the boat
I went out and looked at mine. Same light but on a 2000 265 Express.
The 4 wires to the light are red, black, blue and dark gray. I have to admitt I was confused by the dark GRAY wire. I'm wondering if that color changed over time.
So the Black goes to the negative bus on the fuse panel in the hardtop and the Red goes to a fuse on the panel.
The Blue is spliced to Blue/white and goes to spreader lights
The dark gray appears to be the positive feed for the spreader light switch and goes to a fuse on the panel.
I did not open up the light to see the connections
So it appears that Grady or the previous owner separated the power for the spreaders from the power for the dome lights.
I expected blue/white to come
out of the dome to go to spreaders but it connects to Blue outside of the dome light
I'm assuming the red wire feeds the dome light switch and the dark gray feeds the spreader.(spreader uses heavier gauge wire)