I like retainers at different colors like green, blue or red. But the red shades like me at the time best. I particularly like the see-through (transparent) Retainer. What are me do not like colorful Retainer that have multiple colors. Even pictures on Retainer I think that is wrong. Because I liked several colors I can tick no concrete answer.
I don't think I could pick a single best of favorite color. I like just about any color with glitter added in whether clear, pink, purple, or even bright fluorescent colors. There are too many choices to pick just one!
I also got mine in clear acrylic for the same reason. My bite plate doesn't have a front wire and although the plastic is level with the edge of my teeth, I didn't want it to be too obvious for full time wear.
Also have natural flesh pink Hawleys.
Voted clear red, but there's something to be said for purple as well. Of course, when I got a plate when I was a kid, I was too scared to pick anything other than the normal color. :-[