Entirely from memory, I think that for a ship-based aircraft the upper surfaces should be in a disruptive pattern of Extra Dark Sea Grey and Dark Slate Grey. These two colours are so dingy and alike in tone that they may look one colour in a b/w photo. The undersurfaces would be in Sky, a sort of duck egg green/blue.
Walruses also operated, mainly land-based in North Africa, in the conventional RAF Dark Green/Dark Earth.
As I noted in an earlier post, the proportions of the roundels and fin flash changed in about 1942.
You can buy accurately matched colours from White Ensign Models.