Unfortunately, there isn't a swatch ring available.
We don't typically use them at our studio, either. Once you use the base selection of colors you get very good at selecting for your clients with maybe pieces you have in stock, or save and mark from previous installing.
I have so many clients travel in for the work that we've become very good at selecting colors for them right over email or FaceTime or Skype and can help you with this, too.
In the ManeMaxx Store, you can make your selection and then even add a photo for us to double-check your color selection for you. We will call you if we think an alternate product would be better. You will select a color (pink arrow) and then find that photo uploading here (blue arrow):
Further, colors are listed here: http://support.manemaxx.com/hc/en-us/articles/208636547-Which-color-extension-hair-should-I-get-