Chapter 4 141 O O NH2 NH2 O O NHCH 3 NHCH 2 CH 2 OH H N NO2 NH 2 Disperse Violet 1 Disperse Blue 3 HC Red 1 Due to their occasional use—meaning use specific to a specific occasion—sales for such products are small compared to other dye products. The dyes chosen for these products typically have bright colors but are designed not to penetrate the hair, but rather to remain on the surface for easy removal. However, they still need to be resistant to rub-off on clothing and other surfaces. The dyes are larger in size than those used for semi-permanent products and are either acid dyes (i.e. with an anionic charge) or basic dyes (i.e. with a cationic charge). Some structural examples of these dyes are offered here: N N OH SO3- OH H3C SO3- N N SO3- OH - O3S FD&C Yellow 6 (Acid Dye) FD&C Red 4 (Acid Dye) N N HO N+(CH3)3 Cl- H 3 CO N N N N CH3 HO N+(CH3)3 Cl- Basic Red 76 (Basic Dye) Basic Yellow 57 (Basic Dye)