The 'rust' will be brake dust, oil and general dirt accumulated and hardened over the years.
Of course when it comes to track regularly traversed and stood on by diesels it would be more like this. This is one of my 1982 photos of Derby.
Also absent is the yellow warning line down the platform. This serves mainly to keep passengers behind the line for: high speed passing trains; keep the area clear so the guard/conductor/driver can have an unobstructed view down the length of the train and to aid the visually impaired where there are no tactile (knobbly) paving slabs set back from the platform edge. I have noticed today around my area (Leeds/Skipton) the yellow line has been replaced by tactile paving slabs.
Years ago when I worked for Thameslink, as part of the many training courses we learnt that yellow was one of the last colours which could be seen by individuals with degrading vision and visual impairements. Added to which yellow is a warning colour in nature for many venomous creatures such as wasps, hornets, frogs and snakes.