That bottom "hook" fin is being sprayed gray. The instructions don't say anything about rivet decals, but they'll be added to matche the other fins.
The model will get a overall dull coat. The silver engine mount will be glued in after that.
I hope to keep the nose cone gloss black. The black area on the front wrap decal should also be gloss black to match it. The launch lug guns won't be glued on until after the dull coat so they will remain gloss black.
I'll follow up with finished pictures soon.