Hi,
I don’t think a tattoo is a good idea for this. Think about tattoos you see on others—how often do they hold their color over time? Most fade or shift color. Plus, when you tattoo over erythema or pigment that changes over time too meaning you might end up with mismatched color again down the line. Also, anyone who gets close is likely going to notice it's a tattoo.
A better approach is to treat the underlying discoloration. I don’t know your exact situation, but I’ve seen redness or erythema in the shaft after high volumes of filler, and that usually responds well to IPL or pulsed dye laser. If it’s pigment-related, IPL also works well. Your best next step is to see a
Dermatologist who can evaluate the cause and offer treatment that gives a more natural and lasting result.
Dr. S