My OTO test kit like all others has shades of yellow that correspond to CL levels from 0.5 to 10 ppm. I have found that at higher levels the result becomes a darker yellow, then orange and even to a brown. Since the OTO indicator is able to produce distinct colors corresponding to much higher CL levels, it would seem that it would be possible to simply supply a color match for these higher levels. Although I'm sure the accuracy might suffer at these levels, OTO testing is currently only a rough indicator of true CL level anyway.
So the question is why no one includes matching colors for these higher CL levels? It would seem that it could be of some value for quick testing when you need to maintain higher CL levels.