Just found this poll - it's interesting to see all the colours listed like this and I think if I were having to choose it might be quite difficult as the range is overwhelming. If it's about seeing them on others then solid strong colours are best - I like them to be noticeable, and why not celebrate your treatment with a bright eye catching colour?
Dark blue opaque. Much as I love ortho I'm not much a fan of retainers in general. I prefer fixed appliances and a sort of "finality" of getting them removed with nothing to come in their place.
Has to be either totally clear or the translucent pink gum colour for me. Although I also appreciate large bulky appliances in a more obvious solid colour like blue or orange.
I never had a choice. Both previous times they were vermillion opaque from 2 different orthodontists. I’m not sure what I would prefer, discretion with a lisp or flamboyance with a lisp.
At the moment, the colors pink-transparent, blue, clear and turquoise are clearly used in everyday practice.
Clear retainers must be very well cared for, otherwise they will turn yellow.
Honestly, I like clear retainers the best because they're easy to use and you can barely see them. But if it's the wire type, a light blue or teal colour looks nice without being too loud.