Everyone has their own preference, style and taste; mine happens to be that of black ink only and small tattoos as opposed to big pieces. That's just my taste however, and it certainly doesn't have to be yours. There is a design about nine inches long and it's a trail of turtles on their way to somewhere or another; they even have turtle tracks in the design. I saw this on a woman's thigh and it looked great. Another man I saw had psychedelic turtle tattoos and they were abstract in design while vibrant in color. My concern over color is that it fades, as all ink does and this is why I lean towards solid black ink (which looks gray or blue as it fades).
For unique turtle tattoos simply start browsing award winning designs to start (I use chopper-tattoos). Once you find a few you love, turtle or not, start brainstorming ways to combine what you've found. If you have a great tattoo artist you can easily take your designs and show them what aspects of each you like and request they draw a unique design for you. Don't be shy or hesitant if this is your first inking - artists love to create unique pieces.