Let me start by saying that each tattoo is getting slowly blurry with time. So, after 5-15 years the most of tattoos need correction. However, this is a gradual process which is not noticeable during and right after the healing. Tattoo can also get blurred for other reasons.
Why tattoo is getting blurry and fading with time?
Tattoo inks consist of oxygenated metal hydroxide particles that we apply in cells and intercellular spaces of a body with a needle. If the tattoo is a high-quality one, the ink stays only in that cells and intercellular spaces where the tattooist wants to have it. With time and affected by light, tattoo ink particles are starting to decompose and after that the lymphatic system flushes them out. It is the reason why the tattoo is fading, as pigment concentration under the skin decreases. Also with time and continuous tissue regeneration, each cell of the skin changes its form and is eventually replaced with a new cell, so pigment particles are also slightly moved. As a result, the tattoo is getting blurry.
Why the tattoo is getting blurry and blue during the healing period?
It is important how deep the ink is applied under the skin. If the tattooist does not push hard enough on the tattoo machine, the tattoo will have the „falling out“ parts after the healing period is over. This is a usual situation and a simple tattoo correction helps to make it up. However, if the tattooist pushes on the tattoo machine too hard, he will reach deeper layers of the skin and the tattoo will get blurry. Also by this he injects the ink into the intercellular spaces far beyond the required borders (it causes to appear “bruises” around the tattoo). Injection to the deeper layers of the skin results in change of shades of the ink. It is caused by reduction in ink concentration at the place of the tattoo, as well as extremely thick layer of the skin above the colored layer which changes all the colors to yellow (the color of the skin pigment is tan). So it changes black (which is actually dark blue) to green.
Influence of poor tattoo aftercare
It is not enough to make a tattoo at a required depth. And the tattoo when the tattooist pushed the needle too deep heals much better with a proper aftercare.