Hi Sising,
Before the PicoWay arrived, it was green and sky blue. I would say that the hardest colour to remove is now red/brown. Black ink is the easiest and most straightforward colour to remove.
However, I have seen an increasing trend in metallic black ink being used. This makes the removal process much more complicated as the metallic pigment tends to reflect the laser energy away. This results in additional sessions to completely remove the tattoo.
In a tattoo removal process, the part that absorbs the laser energy is called the chromophore. When the laser is fired, and depending on the wavelength of the laser used, the chromophore that absorbs the laser energy the most will both burn up and break up.
Black ink absorbs energy at the 1064nm wavelength very strongly. When the laser is fired, some of the pigment will burn up. Since light behaves like a sound wave, the pressure waves generated by the laser fractures the ink into smaller particles allowing the body to clear the debris.
