You should paint the horn with color and clear coat of urethane. First, apply the colored paint to the surface. Let it dry and shrink for 3-4 days. Sand it with 600. Mix clear paint with 10% of colored one and apply to the horn. To match the color of urethane with 69 beep beep horn consult autobody shop specialist. He’ll mix in pigments to create the color you choose from RAL chart. This method works on nickel-plated steel too. I have a bright-yellow truck horn hanging on my garage door.