My fave might be "lime juice", but... it's project-dependent.
The natural follow-on question was "how will full color prints look on it?". So I designed the full-color-est thing I could think of to test it. Also a design I thought someone in particular might like but wouldn't have time to make for herself since her life at the time was empty rooms about to be filled with walls and walls of moving boxes. Here's the file I made and sent to TTG:
Because it's a transparent ink process, the colors will be brighter on a lighter background substrate/ribbon, but I think even the "grey" ribbon is super cool as long as you consider that you'll need to use darker ink colors and a bold design.
Interested in trying it yourself? And in winning your own labels printed for free? More on that tomorrow.