Hafner is known for re-using litho sheet metal - it's cool to see the cab floor made of recycled litho like that.
If I am recalling my Hafner history correctly, plain black is correct for your version with cut out window openings.
There were other schemes used as well - this is from the Hafner era, you can see the windows are litho, not actual openings:
The version below is from the Wyandotte era, after they bought out Hafner. Wyandotte also used a black/silver/red scheme that is similar to the one above, but not identical. The actual Hafner locos (like yours) have a far better motor than the Wyandotte version, in my humble opinion...
You got a good deal for $10!