Hiya,
Your Bofors is a Navy one....so i would make it navy grey.....
Did restore a Bofors excatly like yours when i was 21 and we did put it in a permanent display as a deck gun on a destroir in a musuem.
And yours stil have the nice railings behind it and the strorage bins....those are rare...
Keep on posting photos for us....
Cheers,
Louis