LRV stands for Light Reflectance Value; every colour has one. Pure black being 0 and pure white being 100. With regards to a stairway there needs to be 30 points of difference between the base colour of the floor covering and the colour of the stair nosing. For example if you have a dark grey carpet with an LRV of 6 then the stair nosing must have an LRV of 36 or more. This colour difference then helps to clearly differentiate the step nose from the risers and tread. Correctly chosen products with LRV differences of 30 points will create a ‘ladder effect’ when the staircase is viewed from the top or bottom. This can be of particular benefit to the partially sighted and is an integral way of making a stairway safe.