Welcome to the forum.
"If" your car came with chrome valve covers, the bolts were not painted. The engine was painted Ford blue with masks over the heads where the valve covers went. The masks were removed then the chrome covers with clear zinc bolts and unpainted clips installed. If the valve covers were painted blue, I agree with Jeff, bolts and clip were also blue. There's a trick to that, the painters were sloppy, a lot of missed spots and a lot of overspray.
You might consider letting the other Aussies know where you are located. There is a loose support group of Mustang faithful all over down under. (I'm in Santa Clara, CA, about 4 1/2 miles from the San Jose Ford assembly plant which is actually in Milpitas.)