I really don't use Humbrol for my camouflage but Hu65 is supposedly a good match for RLM 65 as seen on early Bf109 undersides as well as the undersurfaces of bombers and transports. The tropical colour RLM 78 was a slightly different colour designed for the brighter Mediterranean skies. On a model I wouldn't worry about it,I think it would look okay. I doubt anyone would notice unless they come armed with a colour chip!
RLM 79 was a sandy brown and a tan colour sounds like a reasonable interpretation.
Those were the only two camouflage colours on the standard tropical scheme. I'm guessing the "light olive" is meant to be RLM 02,the colour of wheel wells,gear struts,and early cockpits. That colour should be a grey/green.
Bearing in mind the vagaries of colour chips,computer monitors etc you can see that RLM 65 and RLM 78 are not that different here.
RLM Color List
Here's a contemporary colour photo of the scheme and,yes,that is snow in the background. The aircraft have been diverted to the Eastern front.
And a couple of decent restorations,posted with the normal caveats, they are just big models!
Cheers
Steve