Chapter twelve is a short catalogue of ways in which stimulation impairs the faculty it stimulates. The five colours blind the eye, the five notes deafen the ear, the five flavours numb the mouth. Racing and hunting drive the mind wild, and goods that are hard to get warp conduct.
The numbers are not decorative. Five colours, five notes and five flavours are the standard classificatory sets of Chinese thought, and naming them is naming the whole ordered systems of vision, music and taste. What is being described is therefore not excess of a random kind but the fully elaborated cultural product of each sense, which is exactly what a court would supply.
The claim is not that colour, music and food are bad. It is that a sense worked to the limit of its refinement loses its capacity, and that the person who has eaten the most elaborate food available can no longer taste. This is chapter nine's argument about limits applied to perception rather than to possessions.
The final item breaks the pattern usefully. Goods that are hard to get do not impair a sense; they warp conduct, which moves the chapter from perception into behaviour and connects it to chapter three, where the same phrase appears in a political setting. The progression is deliberate: over-refinement first degrades the faculties, then it degrades the person, and then, in chapter three, it degrades the state.