Did more research on this, and checked the shop manual for '58 as well. Firstly, the black and white shop manual pics of the Interceptor engine clearly show gloss black valve covers on a much lighter engine color [block, heads, intake, water pump and oil pan etc]. Further research says that for 1958, the 332 engine was blue, and the 352 was green. Valve covers were gloss black for both. All air cleaners in '58 were Colonial White, which was also an exterior color for '58. Hope this helps, though there seems to be a lot of conflicting info out there.