Stuart Asquith in his recent War in the Sudan 1884-1898 describes the RMLI as being dressed in undress blue with white helmet and black or white leather equipment. I'm not convinced by this and suspect it refers back to the earlier Egyptian conflict in 1882. There is a watercolor sketch in the Victoria and Albert Museum that shows them wearing grey. Crucially, Count Gleichen in his book With the Camel Corps up the Nile, describes them as being in grey uniforms with white helmets and equipment so that is what I am going for.
Two very small illustrations I found on the net seem to confirm the grey uniform. Firstly, this illustration from the official Royal Marines website; you would assume that they would get it right.
Given that they are light infantry I wanted them in rather more active poses and looking a little less regimented. They need a lot of work so I would think that it will take three weeks to get them done. Right, that's enough typing now I better get the rest undercoated!