The tattoo treated will be less pigmented

The object of laser treatment for tattoos is to use a specific laser that will target the chromophore (tattoo pigment) .  Different colored tattoos require different wavelength lasers to achieve the best result.  For example, green or teal colored tattoos respond best to an alexandrite laser

Wherever the laser pigment has been removed, the skin will be lighter in color so dark skinned patients tend to have a more noticeable area where the tattoo had been.  This disparity can often be improved by using a bleaching cream and the surrounding in order to minimize the contrast.