What Nerazim tech do you refer to more exactly?The only gameplay Nerazim tech unit/structure in StarCraft1/BroodWar is the Corsair, as far as I can remember(DTs are not tech, but rather combat soldier).
I don't think they made the Corsair golden because they couldn't make it silver graphic wise, but rather because it looked out of place for it being the only silver grey protoss unit. And yes, it looks out of place in the remake too.
If you want a role explanation I'd say that after the refuge of protoss from Aiur, the Khalai and the Nerazim put effort together to create a new ship. The Khalai created the design and produced the corsair, since they are better architects/engineers, while the Nerazim trained the pilots since their quicker and stealth-ier.
So this is how the Corsair was made, a fast assault ship designed and produced by the Khalai and piloted by the Nerazim. But this is just my speculation.
Also this is official Blizzard artwork made by Peter Lee and as you can see there are three golden Corsairs behind the left Colossus so I'm inclined to belive Blizzard wanted to make the corsair golden in the first place and they look better this way IMO.