I've read black ink is much more easy to remove opposed to yellow or green. That being said could one re-tattoo a light colored tattoo in black for a better results? This is assuming the ink would mix under the skin.
Easier to Remove a Light Colored Tattoo with a Laser if It Was Re-tattooed in Black?
Doctor Answers 1
Treatment of light-colored tattoos
There is no evidence that a mixture of light and dark colors will allow the lighter colors to respond better to laser. The particles of dark pgment woould respond as usual but leave behind the lighter particles. Finding the right wavelength of laser to work on your light pigment is more important.