I am the second owner of my boat. The first owner was a serious racer in class sponsored events. My spars have black plugs and hardware, and I promise you they are class legal. I'd not worry about yours at all.
Just got a new boom a few weeks ago and I believe it has black plugs, your boom should have a class sticker from the factory showing that its a class boom, the color of the plugs definitely doesn't effect the performance in any way