Who cares whether it is quackery or not: these tools have a self-evidently useful purpose which is to manage the white balance of a display as the ambient light shifts between daylight and artificial light. Whether it has any effect on sleep hygiene is entirely orthogonal.

A better analogy would be artisanal water: the touted benefits of their particular magical bottle of H₂0 may be quackery, but the benefits of hydration are irrefutable.