Artists often take liberties with the watercolor style, as there doesn't really exist any rules. Smel Wink makes this watercolor style her own by alternating between brash, sketchy shading to pieces with a softer, brushstroke appearance. Some pieces are heavy on the watercolor style, with no outlines whatsoever.
The blending of colors is pure perfection and precisely what watercolor art is all about. You almost forget that these are tattoos on someone's skin and not just a piece of paper.
Wink's booked out for all of 2016, so you'll have to simply admire her pieces below.
In case you are more into sharper lines, you can find inspiration from Tattoodo's article on Bright and Vibrant Watercolor Tattoos by Yeliz Özcan.