I am by no means an expert on tattoos but this chapter always gets on my nerves (really it makes me laugh) because that just isn't how tattoos work.
Never mind that they are tattooing over fur that can be excused since we can assume they have the ability to tat over fur, or we can pretend melon was shaved off screen. And the blood makes sense because he's getting a tat over an artery.
The thing that gets me though is if he (and the past costumers) are bleeding that much, that means the sloth is cutting really deep, and on pg 11 we can see the sloth causes some pretty bad gashes. At that point it wouldn't even be a tattoo anymore, the color won't show up if you're inking that deep, it'd just be some elaborate scaring.
But anyways I can't believe it's been 2years since this came out, I remember when this chapter updated, man how time flies.