As mentioned, the material was lighter, (linen as opposed to wool) so the figures would not look as bulky - otherwise the jacket was cut the same way. Technically you could get away with painting the European uniform with tropical colours. I'm certain too the trousers were much baggier for the desert climate, or perhaps appeared that way due to the lightweight material.
The biggest difference was in foot wear, and is something that can't be fixed with a change of paint colour. The all leather boots were replaced with canvas, with just the toe and heel in brown leather. Initially these were issued to almost knee length, with laces running up the full length. A shorter ankle boot was also designed from this. Also consider, in the desert the pants are usually worn loose and not tucked inside the footwear.
regards,
Jack