What I am saying is that with current/voltage limiting you can make very high ppm CS, up to maybe 40-50ppm without the CS turning yellow/brown. The reason why is the current/voltage limiting keeps the particle size to a minimum, which in turn gives you clear CS. If you are using a CS generator without current limiting then your statement is true, 5ppm will be clear to light yellow and higher ppms will darken as CS particle concentration/size increases.