The correct colours for the Hunter topsides would be, as Bruce says, British Standard BS381C gloss Dark Sea Grey 638, and gloss Dark Green 641 (new 241).
The undersides up to around 1966 were Aluminium (often called ‘High Speed Silver’) which doesn’t have a BS381C equivalent. After 1966 the undersides became BS381C gloss Light Aircraft Grey 627, because the metallic Aluminium was no longer available when the paint type was switched from cellulose to polyurethane.
Thanks to other forum members, I can now vouch that Ford Moondust Silver (with a coat of clear lacquer) is a good modern substitute for the old cellulose gloss ‘Aluminium’.
From around 1970 the Hunter paint scheme slowly changed from gloss to matt, and white was dropped from the roundels and fin flash.
Another point to note that, say, gloss Dark Sea Grey, isn’t the same shade as matt Dark Sea Grey which has had a coat of gloss lacquer!