I'm thinking this is their casual ink color right? Outside of battle? If so then:

Nami keeps hers a pastel green, with turquoise on the ends.

Serafina's is a deep blue, with a bit of purple on the end.

Riptyde also uses blue, with turquoise patterns.

Shelly tends to keep hers a pastel purple, with teal ends.

Memory can't change her ink color, and always has a lack of pigmentation, so she can't change it from white.
(However if she had a choice...she'd keep them as a nice, soft pink or orange)

Dez's color is a forest green, with purplish ends

Dakota's is orange, with dark orange ends.

Dawn's a magenta, with reddish ends.

And finally, Lion is a golden color, with light purplish ends.