I think the helmet was badly repainted postwar, we cant know why. I have never seen an authentic British helmet paint job with paint running down it, and if it looked gold as The Woodpecker says, we can be pretty sure it wasn't desert camo. Of course it very difficult to judge these things from photographs.
I think the usual practice with desert camo helmets was to mix sand with the paint which produces a very distinctive textured finish, like my helmet here which has been authenticated on this forum, and unlike the helmet featured in this thread which clearly had thin paint running down the side.
Edelweiss I was doing a bit of research this week on my South African mk2 and learned that many 8th army desert-painted lids were overpainted green when the troops were readied for the invasion of Italy after the successful conclusion of the North African Campaign. You never know, your green-painted lid may have been done in the field. If I can find the link I was reading the other day I'll edit it back in this post for you to have a look.
Incidentally, the 70th Anniversary of the end of the North African Campaign was Monday, and the 70th anniversary of the dambuster's raid was yesterday which offers an interesting series of timelines!