We are looking at a stair tread system , specs call for a 70% contrast in color between the nosing and the rest of the stair. So far so good, as I have a spectrometer here. Here is the issue, the stair treads are arc-sprayed material on steel. This means there is a very rough, textured surface that really has no color other than the various irregularities formed by the arc spray. My thoughts are that comparing one base (master) piece to the sample will not give me contrast, but distance between colors (delta E) (is that 'contrast'?) and only perceived color since it is really a reflectance issue, not a color issue. What is the proper measurement system for 'textures' as opposed to smoother 'colored' surfaces?