As every pleo rb is different some come with more paint on their nails than others. I have three pleo rb and one has very dark grey nails , one has almost no grey on the nails at all and the other one is somewhere in between. It is a part of what makes each one unique.
No one knows what the exact paint is that Innvo use when making pleo rb's and they won't tell. So many of us have experimented here on the forums and the latex paint/acrylic paint or ink mix is the best we have come up with so far. There is a pleo rb touch up paint kit you can buy on ebay (or you could in the past) But this only contains a few very small bottles of paint and there is no way of knowing if this is actually the same paint Innvo use. It also doesn't come with the grey colour used for the feet. I think it has a green, yellow, blue and either purple or pink.
Anyway hope that helps.