That’s a useful picture. The original oil was indeed very black. ...
Ok, they must have changed the formula over a year ago. I bought my hub in early 2013, and I think mine came out of the factory only a few months before it reached my hands.
Perhaps it also had some graphite in the oil back then, that would have added black to the color?
Rohloff oil is a fixed, same formulation, only as long as any batch lasts. Every time a new batch is made, the formulation changes on hand of what is available and presumably also on hand of developing information flowing from dealers and hubs returned to factory, plus from riders. This isn't unique to Rohloff: even big name motor oils from major vertically integrated brands (meaning they find, extract and refine their own oil and are thus in detailed control of the mixture in the retail can) is subject to creeping development on the pattern and for the same reasons as Rohloff. I don't know a great deal about oil chemistry but I do remember an Atlas Copco general manager once telling me that the sulphur content of oils from a particular region was higher than anywhere else in the world. If Shell and Mobil etc cannot guarantee the exact, precise same oil from year to year at the point of sale, it follows that Rohloff cannot either. But why should they want to? The oils available to them are not likely to be a retrograde; quite the opposite, they are likely to be better at any step, though probably also more expensive.
On the difference in colour between the cleaning oil and the all-seasons oil straight from the bottle: Heavy crude is black because of the way it is formed from plant matter by time and pressure. At each successive stage of refinement it gets thinner and greyer, until it is very thin and clear. I suspect that both the Rohloff oils would be described by an engineer as "light machine oils" but the cleaning/low temperature oil is lighter because it so thin from further refining than the darker all-seasons oil, each further stage of refinement removing more impurities and therefore becoming more translucent.
Rohloff itself has told us something about their oil, specifically in the warning not to put any old automobile or other non-Rohloff oil in their hub: they need to specify it so that it works with Rohloff's weight-saving filter scheme.