We never say anything negative about any laser but here is an article from the founders of the World Association of Laser Therapist on how not to sell cold lasers: http://www.laser.nu/lllt/pdf/Confounders.pdf
If you study our table showing the cold laser specs, you will see that 99% of the manufacturer operate in the Red or IR wavelengths but there are some fringe manufacturers that say that Purple or Violet light is the something special and that the market leaders like K-laser, LiteCure, Aspen and Multiradiance are wrong. One of these manufacturers originally said their laser would "align your cosmic consciousness". Purple and Violet laser are also best wavelength for treating psychological problems in unicorns, fairies and gnomes. For most other conditions, the jury is still out on the magical properties of purple light. It is used in photodynamic therapy because the light reacts with the drug carrier to release a chemical that can attack cells but there is very little research at this point to show that purple light is even a fraction of the efficacy of Red and IR therapy lasers.