I prefer the paste over the roll-on, as it will not become contaminated with blood, which could increase chances of spreading CAE in goats. (Herd is test-negative since 1998 and I want it to stay that way!)
I tattoo rabbits and registered dairy goats. I use the green paste, tattoo and then use the roll-on to push more ink into the holes. My tattoos last the life time of the animals and are clearly readable. Wear gloves as both the paste & roll-on are messy....tho it washes off easily.
I've been using the green past for about 15 years now. You can't beat the paste in dark eared animals. It's the only way to go. It is messy, so wear gloves.